If you want to get a really clear picture of what your team thinks about their work and about you, send out an anonymous survey. I did this last week and received some really incredible feedback. Some of it was encouraging and some of it was a complete punch in the guts. Overall, it gave us a ton to think about and a list of things we need to improve on for the sake of our employees and customers. It's not for the faint of heart, but I highly recommend it.
For further reference, check out this interview I did last season on the Bold Future podcast with Dave Gray: The Company Culture Advantage