Single player is a great but host migration problems bogs down multiplayer.
Overall:
It's around 6-8 hours depending on the difficulty and how badass you are. If you like Half Life 2 chances are you are going to like this. You can tell Crysis 2 gets a lot of influence by it due to how you interact with the environment and how the levels are built.
Your main character is a silent protagonist with not much of a personality but I guess you don't need to talk or have a personality when you're saving the world from aliens because people love you anyway. You got your armor and stealth mods on your suit which give it a definite unique feel. You can either play the game guns blazing or like a ninja. I personally choose to be like Solid Snake because I got a lot of practice hiding in the shadows ready to stab someone in the throat from behind.
Sound:
Guns sounded like guns and the environmental acoustics were actually impressive. The menu music quality sounds like sh!t. I tried using TV natural speakers and theater speakers and I could hear this "bass blown out sound" everytime. It didn't take away from the enjoyment of the game because I never spent more than a few second on the menu. They probably messed up on the sound conversion for the menu track or they made the media file low quality.
Graphics:
There's a lot of detail in the environment and frame rate is solid, there was never a drop in frame rate during heated firefight that I could tell. There is some texture popping in the later levels on trees and some far off buildings. The graphics seem to be a little too grainy look for my taste but I take for a grain of salt and I think it was done intentionally for some sort of technical aesthetic purpose or just how the engine was designed. I played the game on both a 1080p and 720p capable TV and it looked great on both. The cutscenes are actually video clips and don't look very HD which is a shame because the game engine looks so amazing but it was probably for performance purposes.
Multiplayer
THEY ALMOST GOT IT RIGHT BUT JUST BECAUSE OF ONE PROBLEM THE MULTIPLAYER GOES DOWN THE CRAPPER
One thing you need to know. LAG LAG and LAG.
There is some sort of connection or ping delay which really hamper the experience to the point of frustrating levels. 1 out of 10 games you might find a group where the lag is low but the rest of the time it's a FPS fan's hell.
There is just really too many bullsh!t moments with the lag. I get killed a whole bunch when my hitbox is lagging behind my character so basically they are shooting the air behind me and that happens to be detrimental to my character health or when I'm aiming right at them and I look on the kill cam and I found out my character was shooting 45 degrees off.
I really don't know what is the problem because they tighten up the multiplayer with the 2nd demo but when the full game released it feels like it took a step back to the 1st demo.
It really needs dedicated servers for a game this awesome considering I put over 9 hours on multiplayer despite of the connection problems. I was in denial of how bad lag problem was. (Actually it was more like I was still kicking ass because lag works both ways.) Somehow when I'm shooting someone in Crysis it feels "airy." It's not like that Killzone or Battlefield "meaty" feel. Until they patch the connection problems I can not recommend this game for multiplayer only, but single player is highly recommend.
UPDATE: The lag is attributed to host migration problems. The game doesn't do a very good job at picking the host and it tends to pair people up from all over the world regardless of region. Playing around morning time on eastern standard time seem to be the best for me chances are you would land in a low latency game. It's pretty good all the way up till 5pm that's when the latency is all over the place.