Enterprise class framework and tools.

You can knock Microsoft all you want, I do, but .Net and C# are great. And have you opened Visual Studio 2010... I'ts the best IDE out hands down.

Free as in beer...for three years.

Microsoft Bizspark offers a variety of different programs for startups. You can get the software you need, the hosting you need, and even introductions you need. That is if you meet the requirements, but I would bet a lot do.

I know it.

Therefor my ramp up time will be less than if I were to use something like PHP. One of the driving factors in startups is speed... Especially in a competitive market.