We just took the tour at the Old Hundred this summer. It was the first time for me and the family seemed to enjoy it also. The girls got a kick out of panning for gold. Well I should say panning for silver.
I always thought that a ride up the SG&N grade would make for a scenic and fairly short trip. The problem would likely be trying to get the grade up to the mouth of the canyon. I've been exploring the grade quite a bit on the last few trips. The SN is likely a more acheivable goal and it is also surrounded by many more historic structures and artifacts. I like the SG&N though for the natural beauty and it seems to be the road less traveled (at least when I have been there). Add steam power though and it will become another foamer road.
Dave