I don't know if it will make people feel better but I ship a lot of packages and i go years between lost USPS domestic packages. I did have one go missing a couple weeks ago and it was the first one in probably 3000 packages if not a lot more. It was marked as delivered by USPS but asking them to investigate the GPS location for the delivery scan was not correct for the address. Either the local carrier stole it or he made a pretty bad mistake and dropped it to the wrong location and then the person at the mis-delivered address kept the package.

International is a different story. Its still rare one goes missing but your chances are far greater. Maybe 1 out of 500 international go missing. Usually tracking just stops updating once overseas and then its gone forever.

Overall USPS does a good job and offers the best price for smallish packages under a few pounds and for sure anything that can go USPS first class package. Unless you are really big its hard to get a good rate from UPS/FedEx.