Earlier quoted context omitted.
I'm confused about Bundler and rvm's per-project ruby and gemsets, what's the difference?
In my opinion, Bundler deprecates the need--or at least the need in most cases--to use gemsets. They are still a great feature to give you great control over exactly which gems are installed for testing purposes, but once you switch your applications to using Bundler, there's rarely a need to keep each project in its own gemset. What Bundler does is establish a container for all gems (and ONLY those gems) that your a…
rvm gemsets are still a great way to have a general purpose Rails 2 setup and Rails 3 setup on the same machine. Granted, if you only work with applications that use Bundler, it's totally unnecessary. But often you will have legacy apps, or you just want to hack around quickly on some code without set up a Gemfile.