Honestly, the biggest problem I've found with not having dedi servers has been from the administration and social aspect. I can't remember lag being an issue more than a few times, and as I'm on a pretty decent connection, I often ended up as the host.
One of the things that occurred to recently, was when I started playing Bad Company 2 again after a long break. I found a decent server-host to favorite (this was about two months ago), that had a bunch of people that pretty much only played on those servers. I like the servers where no weapons are forbidden, and really the only rules are to not cheat, and behave in the chat. After a few weeks, I also applied to be an admin there, which I am now. The difference between playing on un-moderated MW2-servers where people can scream swears and insults as much as they like, screaming "FUCKING NOOBTUBE FAG" for using grenade launchers and the likes, compared to playing on a server with people I have gotten to know, who understand the importance of actually behaving in the chat to be able to enjoy your time on the server is just incredible. The same server-host (not gonna say the name, this isn't an ad after all) also host Black Ops-servers, with the same rules as our BC2-servers, and you can really see how used people from MW2 are to behave like shit when they go on to play Black Ops. The banlist is a looot longer, and whenever I have a sudden decrease of logic thinking and decide to go on Black Ops, I always end up being pissed off at people in the chat, and talk to one of the Black Ops-admins to go on there and sort things out.