I can't recommend RubyMine enough. It's single-handedly the best developer tool I've ever had the joy of using.

It handles RVM and RVM gemsets natively with ZERO configuration, integrates with Git history and pending changes, can connect to databases and view records IN THE IDE, you can open a terminal right there in the IDE for when you need to get down and dirty.

And the shortcuts - dear lord the Shortcuts are a TIME SAVER. Cmd+Shift+O > Type in filename > Bam. You're there. Cmd+click object, you are taken to it's implementation or declaration automatically.

Highly recommend RubyMine!