Got into Crysis the other week and am left with mixed feelings.
First I love the graphics and the gameplay on all levels up to Core. Core and onwards well they can just be forgotten as bad dreams. They are all linear, with no freedom to choose what you want to do. Before that though the game is wonderful.
Running at 20-30fps on High settings with custom tweaks to a few things. So performance isn't so bad. Only get stuttering on sections where Ice and normal landscape mix. (Running a Phenom 9850BE, 9600GT, 4GB RAM and 600GB RAID 0 on a M3A32 Asus mobo)
After completing the rather short game on Delta first pass I went back and ran it again using the Natural mod. It was so much more intense than the first time through. The night was so dark you had to use NV to see the enemy. Movement was slower due to having to check about you more often and the visuals for things like Contact and other spectacular scenery were so much better than the standard version. For example the level Recovery where the second part is to follow a river to meet Prophet, instead of a yellow tinge to everything it was crystal clear and stunningly beautiful where before it felt heavy and dull. Can't really say anything other than I totally recomend this to everyone.
However that was still too easy and after completing it again I have installed the Realism mod v1.002, which is still WIP. Its very good, gives assumed names to guns and ammo and generally makes you feel more involved in the game. The usage of the different suit functions are more specific, but you still tend to be in either stealth or armour modes. Though Strength now steadies scoped shooting nicely and speed is very useful for traversing sections with no enemies

Only problem I found is that I was expecting it to be harder, but I have found it easier. Oddly enough the guy who made it thinks its harder as do most who have tested it, but then I play a fair bit of CoD4 and that is a lot faster than Crysis and uses much more tactics (when playing online against people) so to compare the AI is a little unfair. The best thing about it though is the guns feel more realistic, though I miss the single shot kills with the pistol chances are you don't get them cos bullet deviation has been increased on the pistol. The SCAR is now a killing machine, as well as the Shotty which was pretty much useless before. The SMG is great too, but can no longer snipe very well

All in all it makes the game play more realistically, but if you are good then using grenades and the right combo of guns + a good dose of skill and you'll smash any combat section. The lower ammo caps may catch you unawares if you decide to do Core with it. I know I went through all my ammo in Core last time and even though I loved it (felt a bit like reliving Aliens) I found it something I would only do once.
All in all so much missed potential in this game, but still great for at least the first 2/3rds.