Riley's has a great beer selection and a fantastic location. I am a big fan of the make your own six pack, and the discount that comes with it! There is a very wide variety of singles to choose from.
Every time I venture in, there's something new to try. I haven't ventured into the upstairs-- my time in Madison has been mostly a beer exclusive drinking affair, and that's contained on the first floor as far as I know -- but I've heard the selection of rarer wines and spirits is excellent.
There is a down side to this wonderland of booze. Every time I try to engage the employees (for a recommendation, to see if something specific is in stock, or just idle chitchat as I'm being checked out) I feel like I'm inconveniencing them. I don't want to be your best friend, guy, I just want some idle banter about this beer I'm consistently dropping money on!
Still, for convenience and selection, I'll deal with silent visits, although I won't stop trying to engage!