I'm glad this thread bounced up, with all the links. Thanks very much, Mitch, for starting and sustaining this discussion, and keeping the focus on vision, spontaneity, and opportunity, rather than limitations of sensors or lenses.
The GRDIII goes everywhere with me because what it sees is not what I was able to see with OM2 or M43. As Moriyama acts out with his SLR-to-the-eye gesture, something gets lost or turns away in that moment. The little GRD has been a Yoda to my bumbling Luke in a discipline of one-handed shooting, hip shooting, quick framing. I came to rangefinders late (58) after SLR and m43, and because the GRD inspired/prepared me for RF seeing/intuition (if not for the laughable difficulties that accompany late adoption of meterless film technology). I've also adopted the GXR/M-mount, but use it mostly with the VF for eye-level/waist-level composing: like an SLR. And though I do like the pair that way--GXR with 50-75-150 capability, GRD for getting close with 28 or 21/1.9--GRD solo is like a favorite pocket notebook/fountain pen.
Dutch photographer Wouter Brandsma's dedicated exploring of the GRD and other small-sensor notebook cameras deserves a shout-out, too, in this thread: http://wouter28mm.wordpress.com/