I think using unmanaged code for performance reasons is one of the worst premature optimizations I've ever heard of. Before choosing any technology that is harder to work with, because it can be faster, you need to be sure that you need speed.
In addition, the CLR is so close to unfulfilled performance that 99 out of 100 cases should not even think about it. And even if you end up in a camp that needs performance, you should write most of your code in a managed space, and then switch to unchanged in the parts that your profiler talks about.
: , , AI.