We(team of 25engineers at Maisa) use collection of IDEs in doing our client projects.
Here are our top pics so far: 1. RubyMine 2. NetBeans (we stopped using it after several years of use, because Netbeans dropped support after v7 onwards) 3. TextMate
Our linux gurus use VIM too!
Hope that helps...
I find Aptana handy for Ruby and ROR in general, bacause it has integrated Terminal window/session. It comes pretty handy. I am still catching up all the keyboard shortcuts. Additional benefit is that it is Eclipse clone, meaning you will feel at home if you use Eclipse or lets sat Titanium Appcelerator IDE for development or any other Eclipse clone. VIM has a steep learning curve from my POV, but I see it as very powerful editor for advanced users. I look forward spending some time getting familiar with it. In general I use Komodo Edit which is also multi environment IDE (Win, Linux,OSx) which is also great for Ruby development, but knowing and using multiple IDEs for development surely can't hurt.
NetBeans 7.0.1 is the most popular IDE for rails. Ruby on Rails is available as plugin in NetBeans 7 and above. Add 'Ruby on Rails' to NetBeans and start using.
I have used Aptana RadRails, NetBeans, and Textmate in the past. Now I'm using RubyMine.
What I particularly enjoy with RubyMine is the fast search & navigation, and the superior test interface (which supports RSpec and Cucumber as well as the standard fare). The VCS integration also works well. Its text editor is very similar in behavior to TextMate.
It is a bit of a resource hog; however, the performance has gotten a lot better with v2.0. And sadly, it's not free, but you do get what you pay for.
I am really like RubyMine v2. It is nice to be able to right click and do a refactoring like rename and have it mostly work. By mostly I mean that it doesn't change the name of spec files, but it does update the class name everywhere. It does use up a fair amount of ram, but so far, it has been stable and fast. The other thing I really like is the ability to run individual specs or cucumber features from directly within the IDE.