One thing I’ve been predicting to everyone who’ll listen is that like deployment and scalability, serious IDE support is on the way for Ruby. Learn the language now, reap the benefits of better, easier tools down the road. Looks like that prediction is looking good right now. NetBeans is making serious progress on Ruby refactoring.
In the meantime, Windows developers can pick up Ruby in Steel a Ruby development extension for Visual Studio. It doesn’t support refactoring yet, but once one of the IDEs supports it, they all will shortly afterward. Intellij IDEA has a Ruby editing plugin that doesn’t yet support refactoring. Eclipse fans have RDT. There are a number of other IDEs that are up and coming as well.
Currently, I’m still doing my Ruby development in TextMate, but as soon as there’s an editor that has real refactoring support, I’m certain I’ll make the leap. Tim Bray is right in saying that “find usages” is the make or break feature in terms of refactoring.