To us (PC gamers), MW2 is a huge step backwards for multiplayer, not just in balance but in the service (IWnet) itself. The very big thing about PC were dedicated servers, the fact that we can choose what we want to play and to have the least amount of lag as possible, MW2 just forces you to play certain maps, leaving you only able to choose what gamemode you want to play. Another big factor are admins for a dedicated server, that can ban hackers when they show themselves on the server as opposed to relying on an anti-cheat or a report system to do the banning, VAC isn't that bad, but it's far too slow to react and there are still a shitload of hackers still on MW2.
The lack of modding ability also pisses me off, since that also ties with more control of your game and also adding more longevity to your game since the community would be generating new content, from maps to total conversions. Next thing is the amount of bugs/glitches/balance issue in this game, and I know that all games will have these, but come on, IW made COD4 which was almost flawless in my opinion. Why they ever allowed people to dual-wield shotguns or made a perk that PROMOTED the use of excessive explosives when one of the main problems with COD4 WERE EXPLOSIVES is beyond me.
The player count was lowered for some reason, while lower player count isn't a bad thing, it would've been nice to have the option and I'm sure it has nothing to do with the fact that consoles can't handle more than 18 since I've seen games that can handle 32 to 64 players that are almost as close-quarters as MW2.
Overall, I think the whole "We want you to play the game the way we designed it" is just plain stupid, you should give players control, not take it away from them.