Thanks for the tip - will be checking this out tonight. Double thanks for the MacVim tip - I'm sure I would have been tripped up and off to Google without it.
I have heard positive things said about RubyMine from JetBrains. However, it is not free and some complain of slow project parse times at startup. Disclaimer: I do have an off and on professional relationship with JetBrains.
RubyMine is amazing for large Rails projects. I can jump between methods in different modules, classes even across gems (a simple command-click on the method, class or module name). You can quickly traverse source trees without the cumbersome grep/find that you'd do in a basic text editor.
Running specific tests is also a snap; just place your cursor in the desired spec and command-shift-r (built in support for spork).
I'm not in any affiliated with JetBrains (swear); just a satisfied customer.
urgh... yes I've used it but I was hoping for something a little less 1980's. We can have multiple windows now ;-)
I find it useful to be able to see the current stack, drill into variables, view my code with syntax highlighting, and the current line all at the same time. It helps me understand where I am.
I've gradually moved away from NetBeans as a general Ruby/Rails editor but I often came back for the great debugging support.
Any suggestion for alternative Rails debuggers?