they're getting better
Microsoft has taken security seriously for a number of years now, really beginning with Windows Vista (as awful as it was).
They are still not as good at it as they should be, but I'm optimistic about their future especially once Balmer is history.
The truth is, many corporations rely on Microsoft products from the data center to edge to the desktop. Anything that Microsoft can release to make sharing security information among other applications is great. The fact that they are using industry standards like STIX, TAXII, and CybOX is just a bonus. For once they are not reinventing the wheel. Of course it remains to be seen how they implement it, but it bodes well for interoperability.