I have an iMac with a gigantic screen and Mac OSX Lion standing on my desk.
The first problem was to get Ruby 1.9.2 running w/RVM. It almost worked minus the segmentation faults left and right, XCode 3.2, 4.1 or 4.2. RVM is not smart enough to tell you that a compilation segfaulted – it just hangs - you have to watch .rvm/log/ruby…/make.log. The fix was described in http://stackoverflow.com/questions/6985690/problem-installing-ruby-1-9-2-on-mac-os-lion, use GCC.
CC="/usr/bin/gcc-4.2" ARCHFLAGS="-arch x86_64" ARCHS="x86_64" rvm install 1.9.2
I ended up adding CC, ARCHFLAGS and ARCHS as exports to my ~/.bash_profile, permanently.