I am very fortunate to have a super reliable and great mailman, and have had no issues whatsoever with the PO (other than a few dented packages). But nothing late or missing in transit, knock on wood.
UPS is the carrier that continually drives me nuts. Every time I receive a parcel from them, I'm reminded of this guy...
https://www.youtube.com/watch?v=5b1aRop-UbU