I like many aspects of this language, but why should I pay money for REBOL/Pro when I can get system access and much more in free and open languages like Ruby and Python? The business model of "charging money for bare-bones interpreters" fell out of style years ago.
REBOL embodies some interesting ideas. I can certainly see why it's rebellious; it looks as though the designer looked at every popular language and decided to take the opposite approach. In some cases this formula works brilliantly, but in others it seems like folly.
Best of luck to the revolutionary guard. Hopefully there's enough features and affordances in this language to attract mainstream programmers once the underground rebolution subsides.