Ignore these guys, they haven't even gotten the game and played it. It's an awesome game despite the MP flaws that everyone acknowledges. The lag is minimal because IWNet is designed to place you in the lowest ping game, and playing a game with friends (8 others + you since maximum game size is 18 players) is simple and works well. Lean is completely unimportant, no serious player in a game as fast paced as this would consider the lack of lean to be important enough to not buy the game. It's well worth 10/10 for MP alone, not even considering SP which is fantastic and replayable and the special forces missions which are fun to play will take a while to complete as some are really hard.
tl;dr - Ignore the whiners, get it and try it for yourself and you won't be dissapointed.
Ignore the apologists like this "Meadows" figure who seems happy to bend over and let the companies ream him/her for a measly 5-8 hour single player campaign with a crippled PC multi-player function that has taken a massive step backwards by using 10 year old internet gaming setups. Despite what IW and Activision may claim, this is hardly in the best interest of the PC gamers and it certainly doesn't offer an even playing field for PC gamers as the host PC will always have a superior connection than those whom are hosted by it; in other words: the host player will have better ping rates than any other player could ever hope to achieve. This sort of lame setup was abandoned a decade ago and with good reason. This latest ploy is likely done in the interest of the companies so as to more tightly control what you get, when you get it and to ensure that you have to pay for new maps, etc.
Avoid this turd of a game at all costs unless you get it free of charge or below 15.00 quid! It's not worth more than that. Oh! And stay away from second hand PC copies. In order to play this game you have to register it with Steamworks which means that second hand copies are effectively worthless. Stopping piracy my ass! This about destroying the second hand market. The pirates already have a cracked version up and running online.
I've played 62 hours of Multiplayer now, I'm up to Prestige 1 lvl 12.
I haven't had any problems with multiplayer, playing alone or with up to 8 friends (normally its 5 - 6 friends) and none of us have trouble with pings. We're a group of players from England going across europe to Finland, so fairly spread out. I can think of only one time where as a group we've decided to leave the server because of lag.
The multiplayer has flaws. Not saying it doesn't, and I never will claim that either. But crippled? No, it isn't. It's 100% playable and the 100k+ pc players you'll see playing over the weekend is easy proof of this. Just a pity the vocal few people whining like yourself are putting off other gamers from something as fun as MW2.