..but it's missing all those nice parenthesis that help readibility. :-)

The two knocks I've heard on the language are (1). It's proprietary; and (2). It's a dedicated language geared towards a certain library - the language makes certain things easier - such as internet communication - at the expense of being a more general purpose language.

I played with it for the [link|http://www.angelfire.com/tx4/cus/shapes/rebol.html|OO Shapes] example a while back. Can't say that I was particularly impressed with the OO facilities, but that's not particularly the point of the language.