I'd probably use telepathy-butterfly for M$N.

You can easily live without the plugin UI. Once you have telepathy-haze and its dependencies (libpurple mainly) installed you can then add all your IM a/c's (pretty much everything that Pidgin supports) in the terminal with mc-tool. They are then all available through the N9's messaging app.

You just tap the "chat" button at bottom right and it takes you to contacts. Pick up the contact you want to chat with and away you go. This is how I use my Jabber accounts. It works well.

Caveat: I haven't installed telepathy-{haze,butterfly} or libpurple on my N9 yet (I do plan to), but I can't think of any reasons why this wouldn't work.