Definitely No - Don't buy. They have the hardware side with Nokia. They already have their own software and services side. BBM would be a distraction and duplication, and infrastructure wise doesn't fit where Microsoft is now and is going in the future.
The Blackberry user base that "tags along" with that purchase is a support and PR nightmare for any purchaser. They will be vocal and adamant about keeping the Blackberry way - those Nokia people who are up in arms are nothing compared to the howls and demands and entitlement the Blackberry users will try to impose.
Frankly, Microsoft doesn't need them, Apple doesn't need them, Google doesn't need them. I don't think their IP is at all valuable or worthwhile to any of those three, or else Blackberry would have already gone there.
HP, however, if they are truly trying to work back into mobile, could be a match. Its exactly the kind of purchase that fits HP's previous acquisitions.......