Installing 1.9.2 from source if it is in fact not in the repos is far better then using RVM.

Using RVM anywhere is suboptimal, but using it in production is lunacy.

apt-get install ruby1.9. It's in there.

1.9.1 is there, 1.9.2 is not. But I still the the better solution is to build from source on each machine, or create a custom 1.9.2 package for the machines you will be using. As other comments have pointed out, RVM is held together with string and duct tape and breaks frequently. I haven't dug into the code from this project, but being more testable and maintainable would be one of the biggest wins they could achieve from my point of view.

I have to contradict you (unless I'm misunderstanding you): the debian package named ruby1.9.1 is actually 1.9.2. The 1.9.1 refers to the ruby ABI. Blame the ruby devs for breaking the ABI in a minor version update (1.9.0 -> 1.9.[12]).

That's the goal, and that's why rbenv does not perform compilation/installation at all (there's a separate ruby-build project for that: https://github.com/sstephenson/ruby-build).