It really depends on who is working at the location. I've had great dealings with the post office, and some terrible ones. Our local post office had this late 60's woman working there who had been on the verge of retiring for years and didn't care if people got their packages on time. She was rude and horrible to deal with. Recently a younger woman started working the counter (maybe 40s) who is very nice, helpful, etc.
All that aside, USPS is still one of the most inefficient carriers.