I've been having a great time with it. It's like Flashpoint (open environments and realistic ballistics) + Fable (open environments and RPG elements) + Half-Life 2 (dystopian feel). The atmosphere is really incredible, the AI is pretty damn good - every time I fight against bandits or other enemies, they always seek out cover and shoot from behind it; the mutant AI is great too since they act like animals in the wild would (in packs and in their own territory). It is a bit rough around the edges but I haven't come across any huge bugs and it hasn't crashed yet after a couple days of playing.

Also, it's been known that it doesn't work well with Vista so it'll crash a lot and you will have frame rate issues because of it.