We went to Madison for a friend's 30th birthday in 2006 and pegged this as one of our activities. Fun little brewery, good little tour, and you wouldn't believe how nicely you can get a jump start on your buzz just by drinking constantly from the little beer mug shot glass of samples. Mmm mmm mmm
They have Bock Fest in February - we are planning on making the trip up there this year (last year one of us was planning a wedding and I was preggers, so we passed).
If you're in the area, go for it!