I go for the food , cheap bandanas, and the Mexican wrestling masks. I did find a nice,complete, Japanese track bike there two years back, but couldn't find a way to easily transport it back to MKE. Plus, there is that stolen bike probability to contend with.
Soon to be owner of a matching pair of Rock Lobster CX machines, Kelly Deluxe, Bianchi Commuter, Waterford R22
I have been pretty regularly for the past few months and haven't seen anything that can't be had at working bikes. The guys working their tables can be kinda fickle on pricing as well. One week it might be like 10 bucks and the next 50. Some of them are really set on their price, but most will be able to be haggled down if you are persistant. On the other hand I dont know of anywhere else that you can get three packages of socks for ten dollars any more readily.