I've just finished Crysis: Warhead. I played it on hard all the way; being a hardcore gamer for more years than I dare say, I don't want any cakewalks while sitting in front of my computer in my leisure time.
As far as I know, there are no achievements in Crysis: warhead. If there were any, surely there would be one for finishing this game in hard mode from start to finish. It's weird how simple things as achievements can increase the interest of a game. In fact, achievements add some really easy to implement replay value. No such thing here.
Crysis: warhead may be a great game in many aspects, but it is also a small underachiever.