While I am a confirmed Microsoft hater, the one place they shine is in providing an environment (.NET + SQL Server + whatever) for the building of medium sized (10 to 1000), internal, pointy-clicky applications. There is no equivalent in Unix or Mac, and this is a massive market -- all the lower level office workers who get some small data thing from somewhere (a customer order, a change order, whatever), enter the data after a little bit of thinking, and move on.

I am a data analyst forced to work on MS environments, and it sucks ass (I have a parallel Unix toolchain installed, plus we use SAS (which sucks ass, too, but that is a different story)). It would suck ass if I was building and deploying internet apps. But for pseudo custom form based applications designed for non-programmers to do glorified data entry, it rocks.

Also, there are probably 40 million "analysts" who don't even know what scripting is and are utterly dependent on Excel, even though they could probably increase their productivity 100-fold if they got a little bit of command line and R and SQL under their belt. However, they don't even know they have an alternative, so Microsoft is totally safe in this zone for at least a few years.