Muskrat makes some telling points. I remember being told that any military personnel who get deployed could send a letter home for free. We were told that we could write it on a piece of cardboard from a C-ration box and, as long as the address was legible, it WOULD be delivered. The US has one of the cheapest postal rates in the country. The USPS moves mail across half a continent as well as international mail, which the USPS pre-sorts for many countries. It really isn't that bad.
There ARE bad post offices. If you have problems with one, report it. Postmasters are held accountable if there are enough complaints. If you don't believe me then consider this, if you are defrauded on a mail order, who would you expect to pursue the issue more vigorously, the USPS or the local police. If the USPS is aware of problems, they will clean their own house. As with anoy complaint, making your statements in a clear, calm, rational manner is much more effective than ranting. Problem reports should contain all of the relevant info but not how annoyed you are because the baby was screaming and traffic was awful. Time and similiar details is very useful. Did you get treated rudely by one clerk? Did you get the clerks name? If you can't, get the time off of the clock in the PO and note which lane or station they are manning.
Regards,
Ed