Messenger by Miyowa is the official Live Messenger for Windows Phone 7 and it jut got updated. You can now get push notifications, dynamic tile that tells you if you’re online or offline, you can change your wallpaper and you can save your messages. Great start. Unfortunately when I log on it logs me off of my PC, so despite the fact that you are able to log in to multiple locations using Messenger typically, the phone version doesn’t do that. So it’s ok on the go but not really the companion app it can be. Keep moving it forward and file sharinge/video chat would be nice – I don’t care if it’s one way only, this should be a major part of the paltform so don’t stop now.
Anyway, check for the update if you have the app installed.