I've been trail running for a few months now. It's a fast growing sport, certainly in South Africa, probably because the combination of beautiful mountains and great weather makes it pretty spectacular. It's also great exercise - lots of hills, and lots of variation. Where running on the road is pretty fixed, on a track you are continually adjusting for the slope, the terrain, rocks and roots. My theory is that the variation in movements is much better for your body, especially the back, which is my concern.
I've joined a regular group that runs on Thursday nights. On a good week, there are about 60 or 70 people in 3 or 4 groups. Tonight was Signal Hill - out & back from Kloof Nek. It was mostly single track, so my legs are whipped from the plants, and knackered from the hills. The mileage doesn't fit in with the schedule at the moment, but I reckon it's good speed training or something. The views from the various bits of Table Mountain that we run on make it all worth the effort.