Should you need any more indication that Crysis Warhead is worth the money, Gamespot's posted a review score of 9/10. Snip:
Warhead's single-player campaign should take you no more than six hours or so to complete, but not only does it invite multiple play-throughs, it costs only $30--and doesn't require you to own the original. In other words, there is no reason why anyone with a capable PC shouldn't play Crysis Warhead. It's more focused, it's more intense, and though it doesn't provide as much of the sandbox feel as Crysis veterans would wish for, it still delivers on every other front. Play this game.
We're properly sold. Full thing through the link.