I do run - about 15 miles a week in addition to my bike commute to work so that isn't an issue. The mounts/dismounts and barriers look the most intimidating. Also, I don't have a mountain bike - I have a commuter bike which I have no idea if it would work or not. I'm wondering if a cheapie Wal-Mart special mountain bike would work just to see if its something I could really get into! (which I'm very afraid the answer would be yes!!!) Open to any suggestions! I did talk to one of my LBS guys who races 'cross and he said the same thing you did about the C class races. Our season starts up again about March - so this is something I'm thinking on very heavy! Appreciate your insight
PS: I have never ridden MTB either and I have never raced. Always a roadie/commuter rider but I love to hike, run and ride so 'cross looked like the perfect combo.