Mess happens. Sometimes it can be the post office in your area being less than upstanding, but generally speaking I have had great service from them here in Philadelphia.
I regularly (as in a couple times a month) mail letters and packages as far away from me as California and Oregon and they are delivered within 3 days. Sometimes sooner.
I also worked as a temp at USPS during the holiday season in 2003 and I worked as a regular employee for UPS at a sorting facility outside of Philadelphia in 2006 for a summer. The level of efficiency at the Post Office runs circles around UPS. UPS could never handle the volume that the Post Office does.
That being said, the holiday season is pretty tough along with the mail carts also posing an issue at times. I remember finding a Christmas card envelope that had fallen off a cart onto the floor of the unloading dock where I worked at USPS. I picked it up and got it back into the stream so that person ended up getting it, but I noticed it in the middle of January. I'm sure they weren't happy getting a Christmas card super late and covered in the tire marks of mail carts, but it happens. When you're moving thousands of pieces per hour it is very easy for one to get lost. Even Amazon occasionally delivers the wrong item...
They do have their bad apples though... Like the postal scandal we had in Philadelphia where they threw mail in the trash or locked it in trailers undelivered because they needed to meet mail quotas, but claimed there wasn't sufficient staff... That was pretty messed up.
Agreed. I've had much worse experiences with the UPS... But with that said, nobody complains as much as the USPS (And in my opinion, they're treated quite well).
In my dealings with the post office, I have had a mail carrier that for years refused to deliver packages (Insisting I was not home). I was unable to get this resolved, as the post office took her side, agreeing that I must just not be home EVER...
I had a postal worker use a sharpy and write all over my wooden mail box and post.
I've had the postal worker throw my mail into the woods (I live in the country).
I've been refused my mail when I've had to come in to the post office to get it. Claiming it was locked up (It's a small post office where everything is visible and no cage exists. I could understand this if they had somewhere to lock something up...).
I've had a postal worker demand that the mail box be moved 4 times. Each time they told me precisely where they wanted it, then she claimed it was wrong.
So, while I agree with you that there are some bad apples in the USPS bunch, they're also impossible to get rid of.