To my mind it's the entire stack that makes it a problem. For example if you don't feel comfortable using Mono, you also have to deal with Windows for your OS,

To my mind it's the entire stack that makes it a problem. For example if you don't feel comfortable using Mono, you also have to deal with Windows for your OS, better experience with SQL server, etc. Even if you use Bizspark to make the up front cost trivial to non-existent, you still have to use those specific technologies. How many of the types of people who are tech people founding startups prefer their servers on Windows? I sure don't, even though my day to day desktop life is there. It just doesn't feel right. But maybe that's just because my prefered languages for personal use/etc are at least arguably better on *nix environments (Python works well in Windows, but Clojure's not nearly as good, at least once you factor in a lot of the popular tools like Lein).