Pros
High compensation (especially considering the cost of living in Madison), very intelligent colleagues, beautiful campus, great benefits, good and cheap food. Everyone is very helpful, willing to take time to help you with just about anything. You can pretty much set your own hours. Rewarding work in a field that directly affects millions of people.
Cons
You will likely work mainly with very archaic technology (VB 6 and M/Cache). Definitely more of a "career" place than a stepping stone for more opportunities, though this could be a pro to some. I often felt I was doing a lot more maintenance of old code than I'd like, as opposed to creating new stuff, but your mileage will vary. Lots of institutional knowledge. It takes a while to get going, but once you do