... but, aside from the higher tool cost, slower development time, and more expensive hosting, it's great? I don't think performance is really a reason to pick

... but, aside from the higher tool cost, slower development time, and more expensive hosting, it's great? I don't think performance is really a reason to pick the MSFT stack; MySpace does use it, proving that it can scale, but there are many more cases of web-scale systems built on open-source tech. So that's, at best, a push. It is easier to find warm bodies for a MSFT shop than, say, a Python shop. But, as a startup, are you looking for 5 great guys, or 50 mediocre ones? And do you really think it's easier to find 5 great MSFT guys than 5 great Python (or Ruby, or Java, or even LISP/Haskell/Erlang) guys? The last point seems debatable to me, the others, less so.