Let me just start off by saying Eldorado is by far one my favorite restaurants in Madison.
I have been to Eldorado a hand full of times already. The biggest thing to note is that if you plan on going on a Thursday, Friday or Saturday night, you will most likely want to call ahead to make reservations. It is usually pretty busy.
The food is always great. I always try to have something new when I go and I have never been disappointed. Brunch is also very good.
One of the really great aspects of this restaurant/bar is their drinks. They specialize in tequila and their house margarita is especially tasty!
If you haven't tried Eldorado, I would highly suggest it