One thing I find myself doing on occasion when trying to sort out gem troubles is removing an entire gem's directory structure, mistakenly thinking that'll get bundler to re-install the gem on the next bundle call.
The problem is Bundler (or actually RubyGems) doesn't check the gem's installed directory for its presence, but just scans the specifications folder for .gemspec files. In order for my little trick to work, I not only need to blow away the gems directory structure in zz/ruby/1.x/gems/
It would be nice if a bundle reinstall command existed to do this.
bundle update isn't what I want since that will update to the latest matching version.