I, too, was interested in the DP-2, ordered it over the weekend and received it Wednesday. My first impressions were much along the same lines as earlier posts, with a couple of differences.
Having spent a couple of hours in a favorite local location taking photographs, I believe that the the DP-2 is much slower than my Canon DSLR's. Over the last 10 years, I've taken over 2000 images in this location, averaging around 70 per trip. Today, I got less than 30. Fumbling with controls, the use of manual focus and waiting for the camera to be ready for the next image were major contributors to this result.
I exhausted the first battery in getting the camera set-up to meet my way of working, like finding how to set the date, setting RAW only, Aperture priority, power-off times and a number of other settings, and taking 41 images. I imagine that the next batteries will last a little longer.
Sigma Photo Pro has a number of major annoyances, it seems to remember settings I'd rather it not remember and forgets settings I'd rather it would remember. It seems to be useful only for setting white balance. Luckily, almost all of today's images were sunlight WB, so setting it was easy. All of the images were then adjusted in LR4. The results were excellent, when viewed on the monitor. I sure wish that LR4 supported the camera's raw data.
I would suggest that, while you a waiting, that you download SPP, search the net for sample raw images, and develop your workflow. That was a great help in dealing with today's work.