I only ship using USPS, 99.9% of the time Priority Mail with delivery confirmation, Express Mail the rest of the time.
Don't have a lot of experience with FedEx.
See my sig for my feelings on UPS. I now warn every person who i do trading deals with not to use them, and anyone who ignores my advice and ships to me using them anyway gets immediately put on my 'do not trade with' list. UPS, Rambus, PC-Chips, and the Abit RMA department are the four enemies of computer enthusiasts everywhere, and i hope that an especially hot place is reserved in hell for UPS in particular.