EVERY time I've been here there has been a line(anywhere from 10 to 20+ people) and only ONE person working the counter. Parking outside is very limited, and often there is a queue.. I try to go after "peak" hours...but it's still ridiculous. Last time I was there, I felt bad for the woman behind the counter(who was really trying to do her best) because the line was literally out the door. Every person in line was pissy, and several people voiced their dissatisfaction.
Bottom line: avoid at all costs. There HAS to be another Post Office in the Madison area that is better staffed.