THE definition of a rehash
the menus - the menu layout for MW3, not joking, is the same menu layout for MW2, with some extras thrown in (facebook login, theater ala Black Ops, etc) it looks like they took no effort into changing anything about the menus, except throwing in MW3 all over the place.
single player - i played through this game on veteran the 1st time, and it goes well with the first and second modern warfare games. i was actually entertained with it for the most part. Playing through veteran is much of a grind as it was with the past COD games...all scripted, throw flash, run and gun, and repeat. Pretty much if you arent going to play on at least Hardened, its no challenge.
multiplayer - SSDD...no joke...didn't change a thing from MW2 besides these few things:
1. Gun Leveling - The more you use a certain gun, the higher the level it goes up. like rank, as you level up, you unlock more parts, perks, and camo for your gun. Max cap is 31.
2. Killstreaks - 3 different setups, Attack, Support, and Mercenary...attach and support are self explanatory, Mercenary is simple, more kills you get more perks become acquired. One thing i did like is that now you can stack up your killstreak rewards and choose which ones to use, unlike last COD where the last reward you get is the one you have to use.
all in all, it feels like this is the way MW2 MP should have been. don't expect anything revolutionary from this.
Spec ops - like MW2 they have the mission modes you and a friend can play through. but the new mode they have is Survival mode. I'll be honest, while it is a fun game mode to play through once you are leveled up and able to use sentries...it is a bit of a grind to get to that fun. But it is worth it. I would also go as far as to calling this Zombies 2.0, being that is pretty much the objective of this gamemode...survive. But this is a good mode to go to get away from the online MP if you even need to.
my final thought - being as hyped as it was, i am not really that thrilled about MW3. I feel almost cheated when i first started the game to see that it could have easily been a $60 MW2 add-on. No menu change, no improved graphics, same game engine as MW2 (including the cancer known as quickscoping). If you are a die hard COD fan, then by all means, you will love this game as there is nothing new to get used to. If you are looking for something new and revolutionary to play in modern time shooters...try Battlefield 3.