I think I'd vote against a full-blown bundle administration feature for textmate. The included bundles are enough for probably 80% of people, they are updated regularly with Textmate's major/minor/cutting-edge updates.
But it's clear that SOMETHING more than the current ad-hoc system for third party bundles is needed.
Perhaps TM could use the 'txmt' url scheme to install bundles? Then, we could have bundles.textmate.com as a cpan/python cheeseshop/rubygems web page with links that automatically install bundles? Seems like it wouldn't be too hard to implement a tm-command that could check versions on the locally installed bundles that could pull from this web page. This web page wouldn't even necessarily be required to host the bundles. Perhaps just official bundles would be physically hosted on this domain. But third-parties could at least create an entry with a "txmt" link to their bundle. Or maybe if the domain could host bundles, we could put a "Publish Bundle" button in the Bundle Editor, that would pop the bundle online.
I've been looking at mercurial and it's nice! I have two computers, and switch back and forth between them from day to day, all while editing two checkouts of the same svn repository. what a pain in the butt when I have to try and commit and I bump into conflicts. The documentation is really good, which is important!
I don't think most of us will have too much trouble picking up mercurial or git. However, new users (the same ones who struggle with svn) will likely have problems. I can't see how these problems would be anymore severe than learning svn.
Glad we're talking about all of this, –Alex