I'm not much of a messenger user but have to use it for work, or so I thought.....
A long time ago I used GAIM and open source multi network client for chatting, the short version is it's an alternative to messenger! They had a legal battle with AOL and their AIM (AOL Instant Messenger) so have in the last few years re branded now their called Pidgin, their site can be found here.
Overall I'd say it's cleaner than MSN which has driven me slowly nuts over the last few weeks with it's bloat-ware like behaviour.
Next thing to try is Trillian... it has few more bells and whistles but is much cleaner than Messenger, Pidgin didn't resolve aliases too well but Trillian got it spot on. I got the client from CNet.