I used Aptana for a while when I developed on a Windows box, It was pretty good, but then I got a Mac, and bit the bullet and paid $50 for TextMate editor. which I love.
To be perfectly honest, I've never really used the prettify feature of Aptana (or maybe is was the refactor feature???), I played with it a few times, (this was three years ago), and I remember NOT liking what happened.
But if you've got $50 to spend, there are a variety of prettifying and refactoring add ons for TextMate (they're called bundles). They are free. TextMate out of the box, without adding any third party bundles, does a damn good job of helping you keep your code nice and pretty. Like Aptana, it's aware of ruby syntax and Rails syntax, and applies colors, auto indents, etc., but does a much better job than Aptana did.
Joe got a job, on the day shift, at the Utility Muffin Research Kitchen, arrogantly twisting the sterile canvas snout of a fully charged icing anointment utensil.