The Nitty is a Madison staple, and although it has a college bar feel, it's still a great place to grab a beer and meet friends. The staff I've encountered have all been helpful and friendly - the bar was packed in the middle of a busy "power hour" but the bartenders patiently and attentively explained the menu and took our orders.
If you're looking for an inexpensive drink, come at 10:00pm for $1 High Life. If you're hungry for food, the burgers are also surprisingly decent.