Yes, I'm using Color Forth. It's not the best part of the package...it took a really long time to learn, and I had to learn its keyboard layout to do so. My philosophy, in general, is, "do whatever you want, but don't change my editor or keyboard." After all, I spent several weeks being unable to type because I was learning Dvorak, years ago. And emacs had a steep learning curve too.

The UI, I have to say, would not pass Apple's muster. It is a completely different way of programming, and I preferred to program on paper for the longest time rather than learn all the weird controls.