Overall conclusion
The DP1 was a difficult camera to review - resolutely niche in its outlook, it was a brave, if not wholly successful, attempt to do something that no large manufacturer seemed willing to risk. We tried to give Sigma credit for taking that risk and producing an interesting, if distinctly esoteric, product. Sadly, we're not in a position to be much more glowing about the DP2, not because it isn't a better camera - it is and Sigma deserve a lot of praise for the improvements that have been made - but because it now has comparatively mainstream competition.
Which to an extent shouldn't take away from the DP2, since most people don't buy a camera and all its competitors - they use the product they've bought in isolation. And, in a strange way, the DP2's awkwardness as a photographic tool may even endear it to some people. The challenge of conquering the camera and the post-processing techniques necessary to get the beautiful images it's capable of will undoubtedly hold a certain appeal for some. And it is a camera capable of producing some great images. Despite the low nominal resolution suggested by its pixel count, the DP2 can capture astonishing levels of fine detail that are comparable with some of the better 12MP bayer designs. And, although the color rendition in JPEGs tends to rather flat and unsaturated, some nice results can be pulled out of the RAW files.
There are, of course, people who will gladly stand on hillsides at dawn with medium format film cameras in the name of image quality and if you're someone with that level of commitment to the cause, then you might find a place in your heart for the DP2. Its excellent rendering of fine detail, such as foliage probably means that it will be landscape shooters who will get the most out of this camera; despite its small size, the need for careful exposure and patience does lend itself more to static subjects than 'street' photography. To be fair to Sigma, the DP2 puts right a lot of things that the DP1 got wrong: the interface is more sensible arranged, features such as a live histogram have been added though sadly it's not noticeably faster.
However, the arrival in the 'small camera, big sensor' sector of the likes of Panasonic and Olympus - companies with a great deal of experience at making polished, mass-market products - you need to be determined to be different if you're going to fall for the DP2. Because, lined-up next to their offerings, the DP2's interface is quirky, its metering has to be watched closely, every aspect of its use feels unresponsive and its white balance is inconsistent enough to pretty much enforce the use of RAW.
Because it's such a niche product, it almost doesn't make sense to recommend (or otherwise) the Sigma - you'll either decide it's the camera for you or you'll wonder why anyone would spend so much money on such a thing. Ultimately though, now you can buy, for not dissimilar money, a similarly small, interchangeable lens camera with a 1.5 stop faster 40mm-equivalent lens that is easier and faster to use, then you have to be utterly convinced by the concept of 'the Foveon look' to choose the Sigma. With its fixed focal length and unusual sensor the DP2's design was never going to be a product for the vast majority of people. Sadly though, its implementation and the appearance of slicker, more flexible products in the same market mean that it's not even a camera for the vast majority of keen photographers.
Above Average
As fotos podem ser usadas a 100% como wallpaper e fica bonito. fazer um crop a 100% de uma foto vinda de um CCD e meter a 100% não fica lá "bonito" 
