When I saw that RIM was using the Dalvik.system as their sandbox engine I thought wow this is a good thing. When I saw 1.2 ghrz processors and captive touch screens I though this might be enough to sway me back. When they announced MS and RIM doing their joint venture i said no way I. H3ll would I come back. I don't want to be restricted to that low of a choice.
Maybe it's more because of the Office 365 cloud based office + BES that's got the two companies announcing a joint relationship.
I'm not sure if you've used Office 365 at all, it's a paid cloud based SharePoint/Office solution for pretty much any sized business. It's very cool... and they are adding BES support soon at no additional cost. Maybe this is part of Microsofts way of "investing uniquely in RIM".
