Umbrella is a card that needs support from many Trojans and their corresponding support cards, but with that support, it can provide incredibly cheap (possibly free) access to servers and a draw engine.

First, let's look at the numbers. Umbrella can break practically any ICE it can interface with for 2, but it can only interface with ICE that have a Trojan hosted on them. Kyuban is the perfect mate in this regard, with this combination allowing for the ICE to be broken for free provided you can front the 2.

Second, let's look at the targets. Valentão and Piranhas are the only Code Gates out of range at this time, but combined with K2CP Turbine or Monkeywrench (also a Trojan) there is no Code Gate out of range. We can do better, though. Egret is a Trojan, and it can turn anything into a Code Gate, meeting both conditions required for Umbrella to work. There are currently no ICE with a strength higher than 7, so with a K2CP Turbine and an Egret, nearly every piece of ICE can be broken. There are a few pieces of ICE that can be raised to a strength higher than 7, such as Pharos, but Hush can bring all of these back down to strength and it is also a Trojan. Further, Arissana Rocha Nahu: Street Artist can install a Trojan during the run, overcoming the weakness of Egret only being installable on rezzed ICE and saving us the click. Combined with Urban Art Vernissage and/or Spree the Egret can be moved each turn, providing a threat to any server.

Umbrella also pairs very well with Ika, which can be moved to a Code Gate for 2 in a pinch if you find yourself encountering one without a way to install another Trojan.

Now, in my books, all of this makes Umbrella worth including in a Trojan-heavy deck. It requires enough MU to support these Trojans, but it makes breaking ICE predictable and cheap, enabling early aggression as soon as an Egret is available. But it also provides card draw for both the Runner and the Corp, during a run, and that makes it very interesting.

For the Runner, the benefits of this are obvious. Especially in a deck that benefits from continuous running through the use of cards like Conduit or making use of Run events, this keeps everything flowing and can put a lot of pressure on the Corp. It also provides multi-access protection against net damage

For the Corp, the card draw can often prove beneficial as well, but there are ways you can limit that as the Runner. First, if you are using multi-access on R&D, like Conduit, the Corp is letting you dig deeper if they draw. This will likely discourage them from doing so. Second, if the Corp is drawing a lot, they are likely to end up with more agendas than they can deal with. Since the draw is happening on your turn, you can take care of any Spin Doctors on the table and use multi-access on HQ like Cupellation to clean up those agendas before the Corp can do anything with them.

All in all, I think Umbrella is a great card that builds a strong board state once a few Trojans are in play, but it can only be included in decks that go all-in on Trojans.