Bike commuting on the Captial Crescent Trail in Washington DC
I commuted often on this trail for awhile and loved it.

Most of the trail is free of vehicle traffic and has bridges going over roads. It's a heavily shaded trail that can provide a nice respite from the sun during the hot summer. Potholes are minimal, though minor cracks from tree roots are not uncommon. Also, there can be quite a bit of debris on the trail after a good wind storm. 

Not too far out of the city the path has a wooden ramp, in good condition, that last about 50 yards.

During the commuting hours, foot traffic exists, but I remember going at a pretty good rate with no issues.

There are a couple poorly lit tunnels, so you will want a bike light.