Wow...I've run this a couple times, at over 3,500 and at around 2,500. Both times I thought it was class II+/III- with the exception of Narrow Falls which seemed to me like a solid III ~3500, but III- at 2500. The run is nowhere near as continuous as Bridges on the Poudre, it's pool drop (except for the miles of scenic flatwater). Yes, most of the run is remote, but if my memory is correct, Narrow Falls (the only place I can imagine causing anyone any problems) is towards the end of the run, which is near a popular campground...
That being said, I haven't rafted it, just kayaked...maybe it's harder for rafts?