I really believe how poor the online is for Modern Warfare 2. And by online I mean servers. You're constantly getting booted or having to wait for host change. Lobbies take forever, sometimes splitting up your party! And then we have the wonderful match's that don't end even though there a total lag fest. I just don't want to hear how much better Infinity Ward is then Treyarch because there not. I never had this problems playing World at War. Plus Treyarch has a fantastic fan site where they track you stats and the developers actually let you know whats going on to fix glitches.
Well there's my rant I'm done. :P