Alright, short review before I head off for the night, I'll do a longer one if requested.

First to address the concerns people had:

Unified ammo - This is needed, the insane variety of weapons that you can get means either you unify ammo or make ammo a non-inventory item with unlimited carry capacity, or the player will be bogged down in ammo shuffling.

Co-op - I'm annoyed that I couldn't do some of the optional missions because they were co-op only, but there weren't too many, and it really has no impact on the single player experience at all.

Purchasable resources - I almost never ran out of resources, except near the end when I had to use scrap metal to make a lot of ammo since I was burning through it so fast. Honestly though, once you gain the ability to scavenge for resources (I'm not spoiling the mechanics of it) you pretty much never run dry, so I'm not sure why they put it in.

So overall thoughts: awesome game, well paced and thought out, some plot holes near the end, but not enough to derail the experience, and a very good length unlike some others (I'm looking at you Crysis 3 and your six hour campaign).

Final recommendation: Buy (on sale would be nice, but you'll get your monies worth even if it's not)