Mac OSX with TextMate. Wanna go back to Emacs, when have time to properly set it up.
Ubuntu with netbeans,,,, i believe its a good combination,,,,,,,,
Gnu/Linux 100% on my 3 machines.
Gedit most of the time, but I like Netbeans sometimes.
I have fourteen Ruby developers in my company (can't say Rails anymore now that some of them are only working with Merb) and the breakdown is: Two on Windows XP, Six on various Linux flavors, and the rest on OS X.
Mac and Ubuntu Linux here. I use gedit, geany and TextWrangler for editors
Intially I was tried with gentoo linux but later i on i was shifted to RHEL 4.0. Because on gentoo and Cent OS i was not able to install db2 express c 9.5 and its adapter. Now its working fine on RHEL4.
I'm using using Ubuntu and Fedora Core for the development and Cent OS for the deployment of the ROR Application. Previously, I am using window XP/Vista for development and Mac OS for the deployment of my ROR/PHP application.