For the most part, Crysis 2 is excellent. I'm glad I bought it. But there are a few bugs I've found:
The "Rifle Laser Site" on the Feline is a bit buggy. Sometimes I'll have both the Iron Sites and Laser Sites to aim with, and in some cases just the Laser Sites. This is not on purpose; the Iron Sites seem to appear and disappear at random. I don't even have to die for them to come or go - they just do it.
Another issue is the lag, but this has been pointed out a lot so I needn't mention it.

Also some sprinting issues... Like sometimes my gun will tilt sideways a lot when sprinting. I know it is held differently when sprinting, but on occasion it'll just bend some untypical way. Once, when I sprinted, the only thing it did was increase my speed to sprint speed. I could still aim/fire while "sprinting".
Also if my gun runs out of ammo and then I melee, it sometimes seems to forget it's out of ammo and won't reload - even if I press the reload button. (Yes, yes I know it doesn't [i]forget[i] it, but it... doesn't detect it's out of ammo.)
Also, why isn't Power Punch in multiplayer? Some people want a stronger melee while others want a weak one. I think a charge-oriented melee would help balance the game and stop the complaining.