Been playing MP while it was "open" (*cough* -- major failure on IW's part here) -- got to rank 32. I thoroughly enjoyed the experience. I played mostly third person team tactical (TDM, CTF, Demolition and Domination + 3rd person) and I had a blast! It left me wanting more, mostly because there's almost nothing for modern third person shooters.
The lobby experiences were great, only a couple times did I actually get a "laggy" game, and even then it was playable.
I did not encounter any hackers (which I feared, greatly) though I did encounter about 1 in 20 people with cheated ranks (not a huge deal, they sucked anyway)
The only issues I had with IWNet (NO, I am not against their loss of ded servers, Modern Warfare is a game suited to small amounts of players, especially on these maps!) were the inability to choose maps, or specific playstyle settings (like hardcore on certain modes, or 3rd person specific TDM only etc) Inability to kick someone wasn't an issue (mostly because of no hackers in my experience, not that I'm saying that they don't exist) The ingame voice chat isn't even horrible quality.
However, SP left more to be desired. Spec ops is badass, until you get 3 stars on everything (not too hard if your team mate is on the same page, though a couple of those missions are pretty damn hard)
I encountered a handful of rediculous bugs (BSODs on exiting the game, randomly) (crazy screen flickering on 1 in 3 flashbangs/stun grenades, unfixable until I flashbanged myself..even then it didn't guaranteedly work) though I suspect them being linked to my 8600GT or my drivers.
Overall, I really enjoyed MW2's MP and it made me desire to purchase the game. It's not as bad as everyone thinks --- HOWEVER, I'm 110% against the $60 price tag for this amount of content. I don't think I could get $60 worth of gameplay out of it... (I got to rank 32 with roughly 12 hours of playtime, max rank being 70/Prestige 10)
Also, IW has been nothing but rude and spiteful to their PC gamers, if they so much as utter a word of grief.
/end review-rant
If you loved the first one, try this one out at a friend's house (on consoles) -- the experience is extremely similar to MW1 and the MP is decent.
