Does performance really matter that much for rapid prototyping/development?
Rapid prototyping for me often involves a couple of lines of code that read in a very large file and do something with it. I have to keep compiling these small programs to native code because the performance of the toplevel is too slow. Then, I have to recompile and re-read the whole file for every little additional thing I want to compute. A high-performance toplevel would help in this kind of work.