We get FedEx on Saturdays....
(Panda get's anywhere from 3-12 packages a day for her work)
Oh and FedEx sucks. Had an incident last week... don't wanna go into details... but they suck
It's not that they won't deliver on Saturdays, you just have to pay out the ass for it. You're looking at next day air, early AM, plus a Saturday delivery fee. For a letter it's gonna be about $75 and a package up to about $140 depending on the weight.
As for their quality of service, there are so many variables it's impossible to predict. Fifteen people will probably handle your package, and some will be better than others. If it has to be handled by hand (funky packaging, for instance) you can expect them to really trash it. During the Summer they have out of school kids working in the warehouse and during the Holiday season it's a bunch of temps. Both of those cause a real dropoff in service. Best of all, their TOS pretty much says that none of their delivery times are guaranteed, so if you pay for next-day air and it takes 3 days to get there, you're SOL-JWF. They're keeping your money.
Best bet is to make friends with your driver. One of ours used to hit the titty-bar with us after work. Another was on our dart team for a year, and was a regular at poker night. They can't keep your package from getting mangled, but they won't give you shit about what they pick up, and if it looks like your package was trashed prior to delivery, they can really help you out. They'll also hit you up at a reasonable time, rather than sometime between 0800-2300.