I fly into Charlotte a lot when I venture over to SC and I don't mind the lengthy layovers at DIA at all.
Douglas International is a medium-sized airport. Your main form of transportation within the airport is a system of moving sidewalks, which does the trick nicely (occasionally you will get the oblivious person who blocks the whole sidewalk, and doesn't stand to the right side and let the walkers pass by).
There are a few really good spots to eat. My favorite is the sushi spot in the main food court area, it's an awesome spot for people watching. The food court (as well as a few other parts of the airport) is littered with white rocking chairs. I think these add charm and they help give DIA it's own unique identity in a way, plus it's a nice place to relax and rock while you wait! There's also a piano in the main food court area as well. I've seen people playing for tips, adding a nice element to the surrounding hustle and bustle.
There are a lot of other airports that have a lot more to do than DIA, but this spot is nice. I won't go overboard with my stars because it's a US Airways hub, and they screw me about 90% of the time.
It's a nice metropolitan airport that has a nice down-home feel to it!