I've been on Pritchett, Green Day, and Upper Helldorado. All great trails, although Upper Helldorado is gnarly as hell.
We didn't register for any of the runs when I went. We just went to trails they weren't going to be running. Those organized runs had really big groups and took forever. My fuel pump actually went out on Pritchett on our way back down (we turned around after the Rock Pile so as not to bounce down a bunch of dirt road) and I had to leave it overnight near Rocker Knocker because the parts stores were closed by the time we got back to town. We went back early the next morning to swap it out and ran into the big organized run. They didn't even want to let us on the trail but we got 1 rig back on, we then ran into the group between Which Way and The Tube, with no room to get around I grabbed my pump and hiked it the rest of the way to my Jeep. By the time my buddy got to Rocker Knocker I had my Jeep running and was drinking a beer watching the chaos at Rocker Knocker. We had to wait for them to all finish there (we got to watch 3 people flop in the process) before I could go down it and leave the trail.