Sorry to seem negative, but what does this give that traditional package managers don't?

The pain of ruby versions / gem versions are often felt by developers who are working with various untested components.

For traditional end users a package manager hides all of this and by typing "pkgmgr install rubyapp" it will pull in stable and well tested versions of ruby plus any dependencies. Applications installed this way should just work without the user going anywhere near rubygems.

So the real value added here is for developers not having to create/manage packages? Surely this is offset by the huge number of issues that working outside of a package manager causes. No shared libraries/dependencies, no universal way to update everything, no ability to manage installations with tools such as puppet/chef, no global mirror network, no assurances of package integrity, ect.