Editor for Ruby?

I'm considering taking the plunge and trying out Ruby in earnest^[*], but lack of a editor is holding me back. Ideally, I'd like a refactoring browser akin to IntelliJ's excellent IDEA for Java.

There is Ruby Refactoring Browser, but it is version 0.0.3 and only for Emacs. Even so, I installed it but am disappointed by the lack of a ruby-mode.

So I solicit suggestions. Any Ruby on Rails fans with help?

* I like the name Ruby in earnest a lot more than Ant in anger. :-)