I gave up on developing RoR on Windows. I loaded an older laptop (Compaq Evo 620 - 512Mb ram, Radeon Mobile 32Mb ram) with Gutsy Gibbon. It runs pretty quickly, even with Compiz effects turned on.
As for editors, I was using a good Textmate knockoff called e text editor. It rocked, and the developer has promised a port to Linux "real soon now". Until that time I've had to find alternative editors.
You are not limited to slow and bloated Java IDE's on Linux. IMO, a full blown IDE for RoR is like 155mm Howitzer rounds for killing mosquitoes.
At the risk of starting the never ending vi/Emacs war, here's my take on those:
vi kicks ass if you're willing to learn 50 bajillion key commands to do anything even remotely useful.
Emacs is an awesome operating system, but it lacks a decent text editor.
To get as close as possible to that Textmatey goodness, go with something like gedit. I have the side file browser, ctrl-alt-o opens the snapopen plugin for quick file searches, and I have a server output screen on the bottom. I have a whole collection of snippets to cut down on time. Shoot, I even have Ryan Bate's Railscasts color scheme.
If you are using Kubuntu, you can find plugins and syntax highlighting to make Kate act almost the same.
Load times for Mongrel are ~1 second as opposed to ~15 seconds on my state of the art Windows gaming rig with XP. I wouldn't even want to see load times for Vista.
If you can't give up/repartition your Windows, I suggest using the VMware player running an Ubuntu appliance. It was almost as fast as a native Ubuntu install.
Check out this shot of gedit set up for RoR: http://grigio.org/pimp_my_gedit_was_textmate_linux
Hope I didn't offend anyone, I was just joking about vi/Emacs/Java (sort of)