I like that proposed "S" system. Instead of trying to gauge rid difficulty, like a ski rating, it gauges obstacle type and size. That leaves it up to the rider to determine how difficult the trail is.

This rating, combined with the trail length, would make it easy for most riders to determine if they will enjoy a trail or not and maybe even estimate the time it would take the to ride it.

So a rider might be able to say "Well, I can handle the 15 mile S-1 at home so I think this new 8-mile S-3 would be OK." Or he might say "since the 10 mile S-2 at home kicks my butt, I doubt I'll do well on this 15 mile S-3."