Aumakua is everything you really wanted Darwin to be.
That being said, there is one thing it's not: a breaker in the conventional sense. Now that Snitch is gone, there aren't any unreasonable combos where you can make Aumakua your primary breaker for getting in to servers. And unlike Eater, it's not particularly well suited for being your backup plan when facechecking big ice. The big turtle is, however, so much more than just a way of breaking that annoying Excalibur. It excels at being two things:
A threat card. A lot of the time, you won't really be using Aumakua at all. Instead, it will accumulate counters as you go about business as usual, and it does so in excellent combination with cards like The Turning Wheel, Aeneas Informant, and of course Maw. The Corp cannot afford to ignore the virus counters stacking up on Aumakua. Once the stack reaches 5 or 6 counters, big ICE becomes paper thin - here the 1 per sub (versus 2 on Darwin) is absolutely crucial. If the Corp doesn't do something about it, then your big turtle will be running anywhere it pleases. The forced Corp response often looks like an entire turn lost to purging viruses, a cost which can be extracted multiple times as simply running like normal will pump your turtle right back up. Combo with Fester to make this tax exceptionally hard for the Corp.
And in a pinch, you can always hit any unprotected server (including Archives!) for extra counters on Aumakua.
A silver bullet for the scoring remote. Criminals excel at finding one-time ways into servers. Whether it's a fraud breaker or simply an Inside Job, a Criminal runner knows how to get in just about anywhere when the price is right. When combined with backup in form of Dean Lister, Aumakua can steamroll past just about any ICE in your way, to swoop into a scoring remote and swipe a marked agenda.
One of the most attractive things about Aumakua is that, at 1 influence, it can bring this Criminal flavor into any other faction for very little cost (its best friend Dean Lister isn't even a Criminal card at all). Therefore, you can get all the benefits above in a more virus-focused Anarch deck as well as in a Criminal build (the Shapers already have a lot of fancy program tricks in-faction). Also useful for cleaning up weak ICE before you can get your whole rig out, Aumakua is a solid addition to any icebreaker suite, taxing the Corp and being the sort of jack-of-all-trades that makes Atman fun, albeit with a very different style.