Why would you want to use C# if its slower than C++?

My last company was founded by 5 C++ veterans with 15+ years experience each. They spent over a month building a certain Windows service. One of them found and dabbled in C#. Within a week he'd gotten further than the collective had in their month. Shortly after, they all switched to C#.

Why C# if it may perform slower: what price do you put on that degree of rapid development?

Why should it be slow ? Indeed, C# is compiled to 'Intermediate Language', which is JIT'ed at runtime, but this can give you a performance advantage, since the runtime can generate the most optimized for the platform the code is running on ...

Depending on the application that you want to write, the 'speed' of the language will have a minor impact. The performance of your application will mostly be determined by the way you design your application, if you make good uses of the tools / technologies you use , etc ... Sure, C# is not a silver bullet, and there are projects where you shouldn't use it, simply because it is not the right tool for the job, but it will do just fine for most of the business / enterprise app's.