My least favorite part is the relatively treeless stretch between Rt. 28 and the quarry. It feels like you're in an oven there on a sunny summer day.
That part always feels like true horse country to me. Very refreshing after the urban slog from Falls Church, something neither the Reston nor Sterling stretch give.
also like the Capital Crescent Trail, although it is a lot more heavily used by all kinds of folks so it is hard to ride at a steady pace. Capital Crescent is even more shaded than W&OD and on Sun., when cars are restricted, you can get a nice downhill ride back to Georgetown on Beach Drive and Rock Creek Parkway.
Ah, my home trail. On a bike, I only use the CCT for the return leg, tho, the outwards leg is River Rd past McKee-Besher then up to Purcellville, race the buzzards down Edward's ferry Rd to the Ferry, down 15 to Leesburg, turn right onto the W&OD at the battery shop.