I think there is a lot to like about REBOL. The native datatypes are interesting. Lots of things like email@adddress.com or http://www.slashdot.org that would be represented as strings in other programming languages appear to be their own types in REBOL. Combined with REBOL blocks this makes creating a domain specific language much simpler.
It’s a pity that REBOL is a proprietary language. The free core software doesn’t have access to shell commands or databases. This makes it a little harder to compare with Perl,Python or Ruby which is what REBOL is stacked up against for competition.