If you want to do this in ruby you can just specify a version manually. If you don't, you still get versions frozen by default with Gemfile.lock. It doesn't pull in anything automatically—by default you get no updates, you can choose to update a single dependency, or the whole thing if you want to verify it works on the latest (useful for libraries for instance). I'm not sure I see the downside.

FWIW I have been doing ruby for over a decade now, and I hold up Bundler as one of the great success stories of open source, and it is one of the reasons I hold Yehuda Katz in high regard, in that he was able to solve a really big problem in the community and hammer it into shape aggressively over a period of two years with a lot of doubters and naysayers (even Rubygems core was against Bundler for a long time), until it finally got so solid for so many use cases (libraries vs apps, private vs public, development vs deployment, etc, etc) where it solved nearly everyone's problems in such a solid way that everyone adopted it.