Looking good. Reading this though, I couldn't help thinking that Bundler and RubyGems should possibly be the same thing. They are both pretty much essential to running/developing any non trivial Ruby application. Why not make them the same so we don't have compatibility problems? This would remove a lot of code from Bundler that is used for supporting a bunch of old versions of RubyGems. It would also pretty much dissolve compatibility problems between the two, since there would be test coverage to make sure everything worked for that version.