After using Jabber for a while, and communicating with my MSN using friends via Gaim I've admitted defeat and gone back to just using the MSN Messenger. Gaim simply wasn't reliable enough communicating with MSN.
After the simple, tabbed interface of Gaim (and Adium on my Mac) the rather cluttered, multiple windowed, advertising bloated affair that is MSN isn't that much of a treat - taking up far too much screen real-estate.
But it's reliable so it'll stay for a while.
I do like the integration of IM, Voice and Video, and connections to MSN Spaces although there's nothing compelling enough there to get me to move from Blogger - yet ! That said as the MSN reach extends to Media Centre and Mobile Phones it could start to become a more central part of the online world. I still like my open Flickr, Del.icio.us and AudioScrobbler libraries though - until Spaces provides a nice open solution (ie with plug-ins for iTunes or Firefox etc as relevant) I'm wary about getting too tied in....