I bike this trail regularly between Columbia and Manchester. Some beautiful views and secluded trails, mostly cool and shaded. Columbia/Andover is grab-bag of dirt, crushed rock, gravel/trap rock, and some large (difficult) trap rock, with width varying from narrow to moderate and some wet areas; Coventry/Bolton is wider, dirt and gravel; Vernon is generally wider, crushed gravel and compacted sand/dirt - very nice; Manchester end is narrow and more of a dirt path. Dangers: some big drop-offs on the sides, at least one bridge out (can work around), some mud, some exposed tracks and bigger rocks. Gradual incline, crests at Bolton Notch.