I'm signed up for it this year and am hoping for favorable weather. I had planned to ride it in spring 2011, however the weather forecast had been for considerable rain in the valley, and I ended up staying home and DNS'ing. It turned out only 10 riders finished the double that year, and if I wasn't even willing to drive/camp in that weather, there was no way I would have finished it.
In my searches of double century ride reports, Death Valley Spring and Fall probably had the most written, so you might try Google as well.