If you happen to be familiar with the MS stack and are able to factor the license fees into your business plan there is no strong reason against and many for using that particular stack.
MS programmers tend to be a bit more expensive than people working with one of the many Linux offerings but that's not such a huge difference that it would become the deciding factor and if anything the MS stack is more performant than the Linux one on the same hardware (and I write that as an anti-MS guy, I strongly believe that politics and tech should be kept separate when it comes to discussing systems relative to each other).
So even if there are lots of reasons why I would not have made that particular choice I can completely understand why the SO people made their choice the other way.