Honestly, I haven't had an overwhelming number of problems in MP. The occasional lag spike, cheater, weird bug, etc... but no more than any other game really. I was really annoyed with the nano upgrade bug for SP but near the end of my first playthrough I had all the stuff the was "the best" anyway. I love the game, it is unbalanced here and there but over all it has been a breath of fresh air for me. I play a lot shooters and always have and this combined two of some well loved games I play in a cool way. The abilities and armor of Halo and the speed, "killstreaks" and the thrills of CoD. I was going to pick up the maps first thing after work but not after the way they have this setup.
To reiterate, I've never had a big probs with this game going over the top with bugs. I don't run SLi nor do I have any overly "custom" configs for my rig so I don't usually run into too many probs now anyway. Nvidia/Intel really keeps things easy, loved my AMD/Ati rigs back when I was strapped for cash, but I'm more a fan of worry free rig builds nowadays. =P Still tons of love for AMD and Crytek though!