Lens choice is limited with Samsung and Sony as well. The main reason I couldn't include Ricoh GXR is that B&H isn't a Ricoh authorized dealer right now, and B&H provided the gear for the shootout.
We've had a few GRD tests on the site. I have a GRD III on long-term loan from Ricoh and plan to write more about it here. Hopefully will be able to get some GXR gear from Ricoh for testing in the not-too-distant future, but I've all I can handle at the moment!