This review will concentrate on the comparing this card to its replacement: Mushin No Shin. We'll consider the player's perspective (is it good?), but also the game design angle (is it good for the game?). Inevitably, we'll get into some thoughts on the philosophy of the Jinteki faction as a result. We'll also use a lot more parentheses than are strictly necessary (I have a lot of asides to make, so I'm leaning into it).
First lets crunch numbers. Assuming that each card takes to draw and to play, that an advancement token is worth , 1 and an install is worth , Mushin offers a profit of , 3, while Mitosis flips the script by paying out , 1. These numbers are more similar than they might have looked on the face of it. Mitosis is slightly more awkard to play, needing some cash up front and two good targets, but it rewards you for your trouble by offering its profits in clicks rather than of creds - a pretty solid upgrade in most circumstances. Added to this, Mitosis is much better with NGO Front, which can upgrade its economic value from 'good' to 'stonking'. The same combination of spread counter distribution and weaker restriction on rezzing also makes Bio Vault a potential target. I've not seen anyone take advantage of this (etr isn't a natural fit for the Shell Game), but it's worth noting.
The shell game
All that said, these cards are not pure economy, so to really understand the differences between them we need to look at the playstyle and strategies they support, which is to say the most divisive deck archetype in Netrunner: the Shell Game, AKA Cambridge Jinteki (AKA "why don't we just save ourselves some time and roll a dice?") Let's get into it.
First, the basic premise: Shell Game decks are those that use very little ICE (some people use none, but those decks can almost always be improved by finding room for a couple of sentries and gearchecks) and instead install lots of unprotected servers containing a variety of agendas, assets and traps. Unless they bring a very strong game into centrals the runner is pretty much obliged to access a few of these installed cards, with the result that they inevitably eat a few traps. The original Cambridge Jinteki used Cerebral Overwriter, and its handsize reducing, damage prevention circumventing threat has been a staple ever since. On the flipside of the coin, cards like Ronin and now Clearinghouse mean that any advanced cards the runner leaves lying around are a potential threat. Mitosis isn't the only boost this archetype has seen recently: Moon Pool can turn the wrong access into a kill, and Urtica Cipher, while not a strict upgrade to Project Junebug has the advantage that the runner isn't safe from it when the corp is broke.
From even before the time Jinteki first became a playable faction (some time around Creation and Control), the Shell Game has been one of its main themes. On the other hand, it's rarely been top-level competitive. Winning Jinteki builds that I'm aware of have tended to range between being economic prisons of the sort exemplified by the old Replicating Perfection decks and 'spiky glaciers' using unfair end the run effects. Cards on the table (to use an apt metaphor): I'm pretty happy about that state of affairs. When I sit down to play Netrunner and instead I'm forced to play a guessing game I always feel slightly cheated and, subjectively, that's my experience of the Shell Game. As such, I'm glad that it doesn't tend to define the competitive meta (yes there are counterexamples, don't @ me).
My snark so far notwithstanding, I think it's important to keep a level head when analysing this type of strategy. Netrunner is a card game, not Chess, and as such it contains elements of randomness and bluff. In fact, it usually contains crucial run/don't run decisions presented to the runner by the corp. Being baited to run a well-protected server that turns out to be NGO can be as devastating as eating a Cerebral. So why does the shell game feel like such a departure from 'proper' Netrunner? I'd say there are two major reasons:
Reason 1: Variance - perceived or otherwise
On the face of it Jinteki feels 'more random' because it presents swingy run/don't run decisions straight out of the gate. You can drop a House of Knives or Snare! on turn one and the runner's decision about whether to check it will have a huge impact on the game's tempo. This feels more arbitrary than ICE, because the runner has fewer cards to address it. If the corp tries to score a turn one Oaktown behind an ICE, then the runner might have cards like SmodCode or Inside Job to challenge it, or they might not. It's a risky play for the corp, but they're not forcing similar perceived risk on the runner. Of course, the runner might also choose to facecheck the ICE without a tool to beat it, but that feels more like a voluntary, calculated move rather than the simple, high-stakes guessing game a naked install from Jinteki represents. Over the course of the game, this initial contrast in challenges to the runner is reinforced. The shell-game deck seems to give away less information, simply presenting more of the same type of bluff plays where a more ICE-based deck would gradually build its board state, affording the runner comparatively more information as a cost for forcing them to build their own board state and economy.
Reason 2: Sicilian Logic
A lot of Jinteki's design puts the emphasis on 'psychology'. The shell game is a big part of this, but it's the psi game that really illustrates the principle at work:
"My best play is to choose 1, because my opponent is likely to choose 0, but they know that, so they'll choose 1, so maybe I'll go for 0 or 2, but they know that I know so they're probably counting on it, therefore I should clearly choose 1... How fun you find this type of thinking has a lot to do with whether you think Jinteki is one of Netrunner's most fun factions or an unfortunate blemish on the game. Some Jinteki players convinced themselves that they're masters of five-dimensional mental chess, capable of predicting their opponents every thought. Grumps like me tend to think it's mostly just random. The fact is probably somewhere in between. Reading and predicting your opponent is a real skill, but even if you're an absolute savant it's probably not that significant.
Applying this analysis to the shell game is extremely instructive as to how it can create a negative experience for the runner. The fully misanthropic take is this: the corp is reducing the game to a bunch of random decisions, and the person playing the corp is acting like that's somehow a skilfull way to play the game. That's not entirely fair though...
There's more going on here
This analysis of the experience of playing against the shell game leaves some less obvious stuff out. It's not as random as it sometimes seems. Less ICE means more access to centrals, and that comes with a bunch of information and opportunities. Have you trashed a bunch of assets? Probably there's an agenda or two on the table. Have you run and eaten a couple of traps? It's likely the corp is holding agendas in HQ you can snipe without too much trouble. There are also situations analagous to having an Inside Job that can challenge early scoring attemps, but they're less obvious because they're about having no key cards in hand. If you've got your deck's only two sentry breakers in hand, you probably want to get them on the table. Conversely, if you're holding a bunch of economy, it may be that what you're actually looking at is hit points. Shell Game decks aren't the best at taxing the runner, so you can afford to risk your Sure Gambles. Basing your run/no run decision on your cards in hand has the side advantage that you're escaping the trap of Sicilian logic. The corp only has a limited idea of what you're holding, so they can't second guess you based on it. When they drop an unprotected remote server, you can look at your grip and ask it, "should I run?"
Any damaging deck is, by nature, going to discrd some runner cards and render their text irrelevant (Yes, apart from Conspiracy breakers, Steelskin Scarring etc - you're very clever). This is another part of the negative experience they can create - people put cards in their decks because they want to play them; having your deckbuilding decisions invalidated off the bat is frustrating and often extremely tedious. However, it's also an observation that can lead to skilfull play decisions. The skill in question is deciding which cards are important and which can be lost. Breakers are useful, but only if the corp has ICE that makes them necessary (and as the Shell Game is generally low ICE, you've often seen exactly the threats the corp has to offer). You need some economy, but not as much as you do for some other matchups, so lower yield econ cards are definitely expendable (meanwhile, you should try to find time to play out slow, high-yield cards like Daily Casts).
Lastly, the Shell Game has always been one of the most silver bullet-vulnerable archetypes. The classic example is Feedback Filter, but Caldera is even better, and there are plenty of 'soft' counters (Steve Cambridge, Buffer Drive and even Harmony AR Therapy are good ways of avoiding running out of cards, while Brain Chip and now Marrow can compensate for Cerebral Overwriter). All this means is that if you dislike the Shell Game, there's plenty of options to "git good, scrub". Maybe it is on the more random end of the curve of possible corp strategies, but it's actually more comparable to proper Netrunner than you might think. There is information, play and counterplay, and runner cards that can fight back against the strategy;.
Wait, what were we talking about?
This is a review of Mitosis! Let's get back on track. How does the change from Mushin No Shin to this affect things? The main change is actually to reduce the swinginess of the Shell Game strategy overall. By splitting its effect over two installed cards, Mitosis reduces the amount riding on any single run. The difference between a double and triple-advanced ambush is a big deal. One Cerebral isn't game ending, and neither is an Urtica. With Mushin it was common to top up the target by another counter, fully loading Ronin or making ambushes into one-shot game winners. With Mitosis this sort of play gives you a two and a three-advanced install, which while still intimidating is much less of a domineering play. Speaking of Ronin, that card is the biggest casualty of the change. The trip up to four advancements is frankly prohibitive without Mushin, and for it to be a useful part of a kill combo, sitting on the table with two advancements just won't cut it.
Overall, though, Mitosis is a good change and good game design. Not only is it a boost to an archetype that's not all that competitive, it also tweaks the playstyle of that archtype towards something slightly less random-feeling and more fun to play against.