Well here's a nice little surprise. After dropping $5 to $4.99 (and ticking off some early adopters), SHAPE Services has just rolled out a v1.1 update to the fledgling instant messaging app. But the surprise is that they added MSN/Live Messenger support, something they previously mentioned as not possible (due to Microsoft's policy).
Evidently either someone was incorrect in that statement or Microsoft revised their position, because you can go and grab v1.1 right now in the Marketplace here. (Thanks, Philipp, for the heads up!)
ps For a laugh, in the Marketplace type in "implus" and see the result.