I have been shooting Dp2 for some time now. I also shoot GXR, Sony a55 and Nikon d50.
In between i have played with Canon 550D.
What is pretty obvious is this. Sigma images that are produced by Foveon sensors are RAZOR sharp and have excellent details and contrast. This is true when u view it even at 100%, where else all other images by other cameras viewed at 100% looks like a splatter of pixels, which some appropriately labelled as "nutella".
When downsizing today's bayer sensors (everyone else except sigma), you can get sharp images but the loss of details are probably large. While one may argue that Sigma images are sharp because they are smaller (4.7mp) this isn't true. They are sharp because that is the sensor characteristic of the Foveon. The new SD1 which is the latest Foveon with 16 mp will display similar razor sharpness at 100% view. Hence the images of Foveon is razor sharp regardless of size as long as u don't blow it above 100% which is common sense.
By now its easy for me to see which review site is trustable and which is not. Any site that evaluates SD15 and did not see how sharp the images are but harps on the low resolution point is not a worthy site. A good balance site would acknowledge the superior resolution of the SD15 and yet give a caution on the 4.7 mp output file.
Any site that evaluates a Sigma camera by using its JPEG camera output doesn't know enough of the overall requirement of various cameras to produce a respectable review.
This is not to say that any site that portrays the SD15 negatively is bad. Go check out the owners review vs the site review and you can see a stark difference. But i am often appalled after googling and reading nearly each one of them, that many missed on the fact that the images are superbly clear and sharp and seems like just one site reading another one's review and modifying the words and often have the same conclusion masked by paraphrasing.