great, IM connectivity, except
I love this quote from the Live Messenger FAQ:
Does this work with all my Yahoo! contacts?Yes. As long as your friends have the beta version of Yahoo! Messenger with Voice, you’re set. When you add them to your contact list, they’ll get all the information they need to gear up and connect with you.
That's like saying "Can I call all my friends with this Nokia 7280 cell phone? Yes, as long your friends have the Nokia 7290 cell phone."
Please - trillian and GAIM, which both kinda suck for their own reasons have been interoperating for some time just fine. Miscrosoft and Yahoo, just make your base IM stuff interoperate. This shouldn't require a client download.