So I actually did my solo trip to DC last week! 3 nights,4 days- I really enjoyed it! Booked a hotel nearish the National Mall on points (Hyatt natl mall) and had a blast sightseeing on my own schedule- it was a short flight on AA from my home airport, easy to navigate and get the metro,I did notice I needed something small and valueless to hold my table at a restaurant if I needed to get up etc, but otherwise it was so relaxing. One main difference for me was the idea that going back to my hotel room in evening meant quiet relaxation, which is different (for me) in that when I travel with friends or family, it's like a hangout,more stuff to do vibe, instead I just enjoyed movie or good tv shows.... I won't hesitate to try solo again after this!