The reason I ask is that I need both 32bit and 64bit under Windows. But I found problems having both dev kits installed. I could only seem to build for the devkit version I last installed - even though I made sure during the setup step to make 64bit devkit setup only 64bit Ruby and vice versa for 32bit.
Also, if there was one location where on could download pre-built binaries I could create a deployment script that would fetch and install.
I should note that I develop Ruby extensions for SketchUp - which has a built in Ruby interpreter. While I can manage to build (eventually) users of my extensions won't have DevKit set up on their machine.