I completely disagree. In fact, my friend and I used .NET our last Startup Weekend event and were the only team to build a complete product against teams using

I completely disagree. In fact, my friend and I used .NET our last Startup Weekend event and were the only team to build a complete product against teams using Python/Ruby/NodeJs. You can in fact write C#/ASP.NET in a rapid hacked together way similar to Python if you want. In our startup products, we've built entire production sites with data stores, front-ends, payment systems, and the core product, in a few weeks. I think it greatly depends on the skill level of the developer. In the end, "startup dev" is mostly tying together a dozen libraries, a datastore, and whatever your secret sauce product might be.