I tried playing Crysis on release when I had my 8800GTS 320MB and it did struggle, so I decided to wait for an upgrade.
When I got my 4870 last July I decided to give it another go and it was perfectly playable at 1920x1200 with high (not very high) settings.
I actually really enjoyed the game (apart from the ending), loved the nano suit functions.
I haven’t tried Warhead yet but am planning on giving that a go soon.
Also will see what my newly acquired GTX280 can do on the original.