Being in the UK I only use MSN (and Skype!), so for me everything else in Adium isn't important. Microsoft Messenger does MSN better than Adium anyway so i'll stay with that until (if ever) anything better comes along.
IMO libpurple sucks for anything other than AIM (and maybe Jabber) and building Adium on it might make for easier coding, but it's the one thing that is seriously slowing development on an otherwise good looking app.
also in the uk and using amsn so i can use the isight.