I've looked at a lot of these different comparisons, and I think Pingflood has it about right. From what I've read, Ricoh GXR tends to be the overall best for using M-mount lenses (especially lenses wider than 30 mm) as far image quality at lower ISOs goes. It hits the sweet spot of having better edges than the NEX-7 and better out of camera sharpness than the NEX-5N.
This said, Sony has the consensus better EVF (both add on and built in) at the moment and better high ISO performance, plus it can operate lenses that aren't strictly M-mount. Also, out of camera sharpness can be overrated. Put all this together and it makes the Ricoh module more of a niche purpose. So not necessarily better or worse really.
I've also read that the Ricoh A12 M mount unit has sold very well (by Ricoh standards), and they may rerelease it with a 16 mp sensor.
As far as comparing these cameras to the Leica M9, obviously the M9 has the advantage of great base ISO image quality and full frame focal lengths and DOF. But it's getting a little old now, and it had an old sensor in it to begin with, it's not surprising that newer cameras can match it in certain IQ comparisons. We had a similar discussion on this forum recently about the NEX-5N catching up to the Canon 5D.
Last edited by Urkeldaedalus; 01-25-2012 at 06:01 AM.