I was at the bike store couple of weeks ago and saw this bike. Not knowing anything about it, I got on it and loved it. I need to keep up with the kids when we go camping, around the hilly neighborhood and some trails (not typical mountain biking trails, more that joggers and walkers go on - not paved) and the beach (not necessarily on the beach) and a thinking this is the right line or me. I have been looking online at the models but am unable to really compare them. Anyone have any insights into the Roll, Roll Comp, Roll Sport, Elite? What's the difference, etc. (I know the brakes, but what else)?