If you plan to have a sandbox like game where the PCs go from place to place just making and telling stories of their own, then this isn't the game you're looking for. While the game does offer a lot to go off of, it is heavily relient on the GM Railroading much of the campaign. All the way down to expecting you to have an NPC that basically drives the plot forward.
Not just that but, the fact that the PCs have to constantly watch the progression of their virus or else die can detract from the game. Especially since using your powers is detrimental to you, as that can increase the progression of the virus which will then kill your character. Sure, you can burn realtionships to push the progress back, but you don't normally have time to befriend every NPC you meet in hopes of not dying by the end of the session. Yes, session as at the end of each you need to check your progression as if it got to high, you die.
You also can't really build the character you want, as the game expects you to have powers that combo into each other. So if you get powers that don't combo, prepare to be dealing minimum damage pretty much all time, while still taking that penalty that increases your virus progresss.
This game does have it's good points though. The setting is very well thought out (even though it can boil down to X-Men mixed with Prototype), the powers are all interesting and cool in their own ways, and it does a good job of giving the idea that the virus is an active one. Plus, if your group likes planned adventures and sticking to an already established narrative/storyline, then this game can deliever on that.
TL:DR: If you like sandbox RPGs, don't by this. If you like Railroaded RPGs, then buy this.