Dave, the proprietor, keeps you engaged as he cuts your hair. The cut is good, doesn't take much time and the price is right. And on the days you don't feel like talking, he respects that (unlike other barbers I've seen that can't stop talking).
I wish the timings were better though - they're not open on Sundays and they open at 10am on Saturdays, which is quite late. I end up going elsewhere because I want an early start on the day.
Overall, if you're in belltown and need a quick, no-hassles haircut, Belltown Barber is the place to go.