By the time Ruby on Rails became popular, Textmate was in every screencast around. But the majority of people used Windows (and a few Linux).
E Text Editor is a clone of Textmate for Windows, compatible with Textmate’s bundles and it costs almost the same thing.
I actually use Intype when in Windows since it’s free while in development1. But E just became more interesting since they released their code in GitHub.
It is not free software, since you still have to pay (and you must not change the license/serial part of the code), but you can improve it for your own needs. This is an excellent example of OpenSource in commercial applications.
1 I plan to use GEdit in Windows (via Portable Ubuntu) since with plugins it is almost at TM level.