Yep, a different game from just pootling around in the woods, that's for sure. Fair play to anyone who races elite - I tried novice, although the fact that some of the others had £3000 bikes and shaved legs kinda suggested that they were anything but.
My main problem seemed to be the downhills - there was one steep one with lots of loose gravel. I fell off on the practise lap, on lap one, and again on lap two. I walked down on lap three ;-) I just couldn't figure out how to control it when the front wheel was sliding about all over the shop...