DP2s or DP2upgrade vs GXR
They are about equal if you average them out. In daylight I prefer the DP2s, the GXR/A12 is better in low light (though it can also struggle with AF). The GXR/A12 and Sigma DPx cameras are my favorites when IQ really matters, but each has quirks. I also have the GRD3.
The Foveon files will be more detailed (in good light). The GXR/A12 does macro. Both make great B&W images. It is easier to use the GXR/A12 handheld.
Neither on is an AF speed demon, but they make great pictures.
Thanks Andrew - a very balanced evaluation - just what I was after. I had the impression at Photokina when switching to single point AF (terminology may be off) the speed of the GXR seemed faster than the DP2 upgrade. It tallies with your observation about Ricoh being better in low light. Food for thoughts.