Maybe TM users should think about creating an open source version. I personally tried TM and liked the general feeling of it, but I won't commit to an editor that (1) is not open source (2) is not multi-platform (3) is not vim :-)
I've personally jumped to Vim. Mostly beacuse I do some sysadmin and now it's much less annoying editing config files, but also so I can jump from OS X and still be able to work.
What I really should do is figure out a way to open sections of text in their own buffer (and corresponding major mode) so that changes in that buffer would be reflected in the original selection.