I commute on the MBT most every day, from Brookland (Monroe and 8th Street) to L or M street, and back again in the evenings. I’ve ridden as early as 7am and as late as 10 or 11pm. I’ve done this round trip since July or so and I’ve never had any real problems. The one time that there was an issue (seemingly drunk person driving on the trail yelling at cyclists to get out of his way) the police responded very quickly. I’ve heard of problems up near Rhode Island Ave, especially with the school kids, but I haven’t experienced anything bad. Way better than my old commute on roads with cars…
There is now a group that was hired to do trail maintenance, and I see them out there several mornings a week- which is awesome! They take great care of the trail and surrounding area.