I've used Ruby on more than a few occasions...made sure to get into it when it looked like it might be the next big thing. Unfortunately, that next big thing never really happened, although it is finally beginning to gain some ground.
It has some excellent features, such as the fact that everything is an object of one sort or another, making all functions methods (of course, that can work against you if you do not have a good grounding in OOP). Plus, the syntax is easy to pick up for anyone with knowledge of Perl.
There are a few things about Ruby that have left me less than enthralled in some situations...it is extremely strict in its boolean interpretations of non boolean data types, and it supports only single inheritance (although there is a way around it).
Ruby is designed to act according to the assumptions and expectations of the programmer, which is a great idea, in theory. I find, however, that if someone were to learn Ruby as their first programming language, the way it interprets a programmers intentions may leave gaps in understanding the lowest level of programming...being able to force a program to do as you wish through careful design.
Overall, I have always felt it to be a good language...two thumbs up!