I don't care much for Ruby myself. I'm a Python guy, but I don't give a frack what language people use.
"Least used scripting language"? Right, because nobody develops on Rails (like it or hate it).
Ever check the stats on Developers who use Macs (vs. the general populace)? Didn't think so.
And finally: that which makes MacRuby very very fast can also make Ruby on *nix very very fast.
The problem with Ruby is not the language. It is the VM. Improve the VM, and more people will look at other uses where Ruby is a great fit but for its speed.