I have so far had no problems with Priority Mail, and from their website I copied this info:
"Now it’s easy to see where your package is at pickup, confirmed final delivery, and many points in between with improved USPS Tracking™."
Free Insurance Included
Get insurance included, free of charge.
Most packages now qualify for free insurance*** up to $50 or $100 for Commercial Plus customers — and that's with current Priority Mail rates staying the same.
Know when to expect a package.
Based on where your domestic Priority Mail package is shipping from and headed, you’ll know whether to expect 1, 2, or 3 day specific delivery.**
they do not GUARANTEE delivery within 1,2 or 3 days, and say that after 5 days its time to call customer service, but I have not had a single package not be delivered on time so far.
I guess I need to keep my fingers crossed