I use vim to develop on my mac and I updated to Mountain Lion yesterday. I was using http://pqrs.org/macosx/keyremap4macbook/ this to remap the escape key's function to caps lock to switch between edit and insert modes. I can't really functionally develop in vim without this and it doesn't seem to work in Moutain Lion. I really need a solution soon!
Thanks a lot guys.
Found this: https://github.com/tekezo/PCKeyboardHack/issues/8#issuecomment-7359829
It worked perfectly for me.
I had grown so accustomed to using caps-lock as esc, that it was killing my productivity until I found this.