Marco, I introduced you to this game.
I must say it's pretty impressive, but you should at least have an 8-series Geforce and a Conroe CPU to play it on maximum settings.
I was a bit disappointed with FarCry and its human-monkey mutants but it was quite fun in the first part of the game. Yeah, I had to play it on minimum settings in that days and I think that will also be the case with Crysis for most people.
I hope the graphics engine will be optimised as much as possible, like the UT2k4 is. I played it on high settings on my old Radeon X600 and was still getting ~40-50fps.
This engine's complex physics will require great computing power so yeah, as I said, you'll need a Quadcore.
Wow, just watched the walkthrough and I can see there are many places where they had a very low frame-per-second rate, that further proves my points.
But yeah the nanosuit and the fully interactible environment certainly make it very interesting a probably very fun. I'm looking forward to it.
EDIT:Oh yeah, are you only going to have one machine gun(SCAR)? Even if it's customisable as hell it would become a bit dull I reckon.