As highlighted by the press, we have indeed been seeing more delays this summer with shipments that include USPS for one of their legs.
A particularly strange thing to watch out for is once in a while (and this seems to be happening all over the country) the USPS tracking number will say it has been delivered, but then they don't actually deliver it until the next day.
So if your tracking number says USPS delivered it, but you don't see a package, give it 24 hours before you get too worried.
On a brighter note, here's a fun article highlighting some of the recent art-stamps the United States Post Office has been issuing.