USPS is phasing out being able to purchase 1st class shipping on packages in many smaller areas and through many private shipping outlets. This has already happened in our area. Service most definitely depends on each facility, as Richard stated, and on each individual employee you deal with. We've had this experience in the past year. From very good service, to terrible, to good again.
In the past 1.5 years, I've had the same experience with odd tracking records, skipped and spotted tracking along the route, though all packages were delivered.
USPS is going through some big changes. Agree with Richard that we should all begin asking for drop-off receipts. For international packages, I've actually taken photos of the packages being dropped off sitting on the USPS counter. :)