It may not be excellent food, but it's one of the only places in Madison open 24 hours, year round, with Christmas and New Years as well. The food is consistent so you know what you'll be getting.
The restaurant itself looks well taken care of, and my visit was clean. The decor looks newly renovated and is much better than other Dennys I've been to, both in the area and out of state.
If it's very late it's a decent spot.