Want to see a showdown between the Zeiss 21mm 2.8 + D800E vs the Ricoh GR with 21mm converter?
See this
post on Clubsnap.
Also, another comparison - this is the bottom right part of the picture (about 30% of the entire picture). Notice how the GR+GW3 sharpness and contrast is just a little worse than the Zeiss 21mm which is prob the best performing 21mm now. All said, i'd sacrifice a little drop in IQ for the pocketability of the GR, though I don't see myself using the GW-3 that much since it's a hassle.
And I think Ricoh is a bloody robber to make us buy the hood and adapter for close to SGD$90 just to use the GW-3 again. They are nothing but two pieces of plastic.
You can download the full pictures here for your comparison.
GR + GW3 vs
D800E + Zeiss.