Related to another open bug, where installation of 1.0.1 by DMG fails, I installed via source without any errors according to the steps outlined in Getting Started. Install appeared to work correctly, by result is a broken library, seen when I run my rake file here:
$ rake -T
/Library/Frameworks/RubyCocoa.framework/Resources/ruby/osx/objc/oc_import.rb:127: [BUG] Segmentation fault
ruby 1.8.7 (2010-01-10 patchlevel 249) [i686-darwin10]
Im using the Mac Ports version of Ruby at the moment.