Just finished the 360 version today. Overall I really enjoyed the game, but I have this love/hate relationship with it. The suit upgrades could've been cool, but I found myself just saving up to get the faster regen and longer stealth. Once I had the stealth upgrade, I kinda felt that I was playing the game "wrong". By the end I'd often just evade the Ceph altogether, rather than risk blowing my cover. In fact on the last level, the only things I killed were the 4 stealth Ceph. And I was fortunate to find a vantage point they couldn't reach, so they just scurried around beneath me while I weakened them with grenades before finishing them off.
I think if the suit upgrades had been done better, the game would've been more like Deus Ex, where I've created a stealth character. With Crysis 2, it felt like I was this tank that was just hiding because it was easier to avoid the enemy than fight them and have them call in backup. But I don't know if that's fair to the game since it maybe has more to do with my disinterest in killing "alien" characters. My favorite parts of the game were when I fought soldiers. In general, I'm not as interested in killing monster-like-aliens, but that's just a personal preference thing.
I was ready to give up on the game the first time I came across the little bug-like Ceph-cleaning things. Thankfully they mind their own business, but when I first saw them I just pictured myself having to shotgun through endless waves of them.
I wish I could've played this on the PC (my preferred platform for FPSs), but until I get a new rig, that won't be happening. The first Crysis was the first game to bring my PC to it's knees, but I've managed to hold off on upgrading so far. I'll definitely re-visit it there if I get a new PC in the next year or so.