Pete, I've shipped around 1,100 packages via USPS in the past year. Most are shipped using third party software/services (endicia) due to the time savings making it worth the modest fee I pay. Others are done using Click n Ship through USPS.com and others yet through PayPal or eBay. All of these online services provide postage rates that are cheaper than if you go to the counter at the Post Office or use stamps and provide Delivery Confirmation for free. Additionally (and most importantly, in this situation), these services compare the address you've entered for the label against the USPS database (for USPS.com and endicia) or confirmed addresses (PayPal and eBay). This would have prevented your typo and frustration. Admittedly, sometimes these verifications steps cause other types of frustrations, mostly because customer/recipient forgets they live on an avenue and not a street, etc. Using these services also allows you to request a pickup of your package by USPS, if desired.
That said, even properly-addressed Priority Mail has been a little frustrating, lately. Towards the end of 2013 and until a week ago I was having a high percentage of packages taking over 3 days (some up to 8 days). My regional rep told me that it appeared airlines with whom USPS has contracts seemed to be playing games with them and turning away packages and saying no space was available.