I've been a long time GXR shooter. You can view my Flickr and photography blog for samples. I simply love it, both using it and the pictures I get with it. Lately, I have returned to the 50mm A12 macro after a hiatus and fell immediately back in love. I'm sure you've heard that they announced an m-mount module. That will be very interesting. Some rangefinder shooters have been curious about the GXR and this is an easy entry for them. I still have one m-mount lens and I plan to buy that module.
At any rate, Ricoh is small and niche, but very high quality. They have consistently been my favorite cameras. They produce outstanding B&W conversions with lots of latitude for PP.
Wylie, I briefly tried the X1 and except for the focal length there was virtually no difference in IQ. The GXR is not as small and light, but it is more durable and the EVF is a must have option that the X1 does not have.
All of my comments here apply to the A12 units. I would not bother with any of the small sensor units.