Imagine my surprise. Christmas in November?
ActiveState's Komodo + Ruby + RoR + Mac OS X?
Haven't tried it yet. It will have to really shine to supplant TextMate. But if the debugging works out of the box (I haven't gotten Eclipses to work yet on my powerbook) and it has good support for Rails, then it could be a contender for the toolkit. Especially given its support for Python, XSLT, PHP, and Perl.