For some time now, I was looking for the right kind of IDE to work with ruby on rails. Googling for this helped but not much.
Eventually, I came across this post somewhere which mentioned RadRails. This is a module from Aptana development studio.
In addition to the fact that this is a component of the Aptana dev suite, this component is available separately as a plugin for Eclipse as well.
And installation and configuration come very very simple. In a running version of Eclipse (I have Eclipse 3.2), look for a remote installation site. Few simple questions about which package to install etc. and you have the plug-in installed.
Here's the url to enter in the Eclipse remote update site...
http://update.aptana.com/update/studio/3.2/ => For Aptana tools in general
http://update.aptana.com/update/rails/3.2/ => For RadRails Plugin
And it works like a charm, really. After installation, you can create a new rails project from within Eclipse GUI as well, in addition to your favourite command line methods.
Starting a server, generating components (controller, model etc..), its all possible from the GUI.
I personally like the GUI and the syntax highlighting the most.