Regarding point 4, is anyone familiar with Xcode 4 and MacRuby? I'm not finding any information on it, and the nightly build doesn't seem to include any Xcode project templates.
The project templates aren't there yet, but should be any day now. In the mean time, everything else works -- compilation, Interface Builder, etc. You'll want to grab MacRuby 0.10 from source or nightlies.