I’ve recently been playing around with Ruby (yes, and Rails).
Though there are still some language issues that need to be sorted out (like variable scoping), Ruby seems to be a very elegant language, with an intuitive syntax (and by intuitive I don’t mean to imply similarity to C/C++/Java). I particularly enjoy it’s poetic terseness: Ruby code is actually readable (for the most part, anyway).
FWIW: I don’t think Ruby will ever be a 100% replacement for Java — and I hope the priests of the Java cathedral are extremely circumspect when it comes to attempts to push Ruby-like features into the language (we could end up with something even more disastrous than Generics!).