Use the Beta, Luke
I don't often use this blog to plug my employer's products, and I've certainly never used this blog to promote a Microsoft product before. But as this has a lot of personal utility to me, I'll make an exception.
Yesterday MS and Yahoo! announced the beginning of interoperability between Yahoo! Instant Messenger and MSN Messenger (recently renamed Windows Live Messenger). Users of either client are now able to add users from the other network and chat to them just as they would anybody else. This is huge for me personally, because I'm on Y!IM all day, and never on MSN anymore -- but most of you guys are on MSN.
So if you're an MSN user, get the beta and then I can start talking to you (or you can try Y!IM instead, but fewer of you will care about that). You don't have to add my Y!IM id or anything -- it'll just work.