Traditional Japanese source of many interesting previews, reviews and comparisons dc.watch.impress.co.jp has posted a very interesting comparison of GXR, GF2 and DP1x at 28mm. Although the article is in Japanese, it's worth to see... http://translate.google.com/translate?j ... 21355.html
The comparison is somewhat unfair to DP1x but the part of the problem lies on Sigma who constantly tries to persuade journalists and customers that the DP1/2 Foveon sensor delivers 14MP files. dc.watch folks took them seriously and developed the DP1x RAW in Sigma photo pro with 14MP resolution. The result is, in my humble opinion, a clear disaster. I'm pretty sure that if the DP1x files would be developed with LR3 or Silkypix to just 10MP, the files would be perfectly on pair with GXR and GF2.
Another somewhat unfair point is that the GXR RAW files were developed with Photoshop CS5 while the GF2 files were developed with Silkypix (delivered with the camera) and DP1x with Sigma Photo Pro. This gave the GXR a very good advantage in low light test, where the GXR files look superb up to ISO3200. No matter how I like the Silkypix, latest ACR does outstanding color noise reduction work and detail extraction. Neither Silkypix nor Sigma Photo Pro are serious competitors here. On the other hand, I don't think that processing the GF2 files (and most probably DP1x files too) with Photoshop would make them comparable with GXR output. Ricoh engineers did a very good job in fine-tuning the Sony ASPC sensor for best signal to noise performance.