I’ve written about the Sigma DP Merrill cameras quite a bit lately, including all three models, as well as the software and ETTR and so on.
My suggestion for those trying to understand if the Sigma DP1/ DP2 / DP3 Merrill might fill a space in their repertoire: rent a Sigma DP Merrill (along with a few extra batteries).
Even if you might think the DP Merrill is not for you, the images are distinctly different enough from conventional cameras that understanding a “true color” sensor versus a conventional Bayer-matrix sensor can be considered part of one’s photographic education.
I like all the DP Merrill models, but the best all around model for pure sharpness and flat field is probably the DP2 Merrill (30mm f/2.8, 45mm equivalent). The lenses are first-rate on all the models, on par with the best DSLR lenses for full frame cameras.