Pretty much same as the old one, but they copied some of Battlefield's challenges & gameplay, very closely
The game is really addicting, especially in multiplayer, because you just can't seem to stop when you keep getting one more goody to light up your enemies with. This is probably the key genius part of the game right there. It doesn't take long to get something new, you can't wait to try it, you have fun trying it, and then you keep playing because you are going to get another new goodie any minute - PURE GENIUS.
Anyway, to critique the game though, its pretty much a redux of the last one - basically new maps, of course, some new weapons, of course, and some new gadgets, perks, etc. Don't expect ANYTHING Earth shattering. The new stuff is awesome and tons of fun, but again, nothing Earth shattering.
Sadly, they totally STOLE the challenges from Battlefield (2), so if you like Battlefield, you'll suddenly find that everything is looking more like a Battlefield title than anything to do with the traditional CoD series.
Even though the CoD series keeps taking on more realism, reminiscent of Rainbow Six and Battlefield, its still does a great job of separating itself with fun gameplay that is not a sim. Overall though, I can't give it more than an 8 as its really just a redux of the first one.