Should you buy the Sigma DP2? Only if you're in love with the sensor. While it's definitely a better choice than its predecessor and is not without its manual charms, its high price puts it in range of DSLRs and other cameras that come without as many limitations.
Looking through a glass viewfinder is such a treat, though—too bad it doesn't seem to actually line up very well with the actual pictures.
If you'd like to download my talking-at-the-camera review that's embedded above, here's a link to a direct MP4 download.
Below, a slideshow of unretouched images from the DP2. (They were shot in RAW, but uploaded to Flickr in JPG, as Flickr does not understand Sigma's RAW format.)