MW2 perfected, but stale and unoriginal.
Visuals are the same, and SSAO doesn't change much at all. At least Treyarch had brought something new to the CoD table with a cold war setting and new (vintage) weapons. Maps in MW3 are worse than MW2/BLOPS. There are still no ranked dedicated servers for PC players.
If you never played MW2 then MW3 will be the most fun you ever had in a online FPS game, but if you come from BLOPS/MW2 you will see less quality, but more balance in perks and killstreaks, yet with inferior maps and the same weapons seen in MW2, MW3 never really gives the impression that it is a new game, but more of a expansion to MW2.