I just received my copy of Acumen magazine with my Fuji Rock Festival images. Great to see they made it the cover feature, and that so many of my photographs were used. The only pic that is not mine, is the top image on the last page which was taken by someone connected to the magazine.
I used the Pentax 645D with a 150mm lens the majority of the time, and the Pentax K5 with a 10-17mm fisheye lens for the wide establishing shots. It is quite tricky to shoot using stage lighting as it can change multiple times a second. To get the best shots, use manual exposure and expose for the light on the artists face rather than the dark backgrounds or the bright flashing lights.