I'm only through the first 3 missions, so I don't have enough to make a full judgement, but here are some things I like/don't like so far: 
 
Like: 
 -The mechanics/engine.  The controls are good, and shooting works really well.  The buttons are only slightly different from other FPS's, which is a good thing. 
- Gun selection.  Already I've used several guns, and they've all had good pros/cons. 
-Achievement pace.  I've gotten some achievements for story, some for other things.  It seems like one pops about every 20 minutes or so. 
-Visuals.  The colors are very vibrant and the enemies contrast with teammates.
 
Don't like: 
-Health.  There's not a good indication of when you are about to die.  Sure it gives you some red border, but it's not enough to tell that you are in critical condition. 
-Grenades.  You can't tell where they are.  Having a guy yell "Grenade!" does nothing, just makes you panic for a second. 
-Destructible Environments.  Not that I'm against the idea, but it's frustrating when you can't find any cover because the enemies just blow it away immediately.
-Lack of coop.  You play in a squad with 3 other guys.   Why can't these be real people? 
 
 I've heard that the real appeal to this game is the multiplayer, but I just don't see myself getting into that.  This could be a game I trade very quickly.