If I suggest one place to visitors from out of town, it is The Old Fashioned. This is a uniquely Wisconsin deal with good food and an excellent beer selection.
Their menu selection is fair. The sandwiches are decent, salads are only ok, cheese curds are good. The beer selection, however, doesn't disappoint. They boast around 50 taps. You can take your pick of some great Wisconsin beers that are hard to come by elsewhere in Madison (O'so, Pearl Street, Steven's Point, etc).
It is busy on Friday and Saturday nights so plan ahead! Sometimes waits are 1 hour + at these peak times. This isn't a bad place to stop after getting dinner elsewhere. Just arrive after 9pm on weekends.