I'm aware that I've had to a ton of customers who have tried out giving large chunks of our volume to FedEx, especially ground, that have not only come back to UPS, but in some cases, given us their total shipping account - this is not usually because of their delivery side, I'm told, but because they're unreliable and often times wildly early for the pickups in the afternoons.
An example of an account they've taken, that cannot wait to return that volume to UPS, is the Department of Defense - Defense Logistics Agency, which is a huge shipper, and a very high discount account - the shipping manager at the base I deliver on, has told me repeatedly that switching our old air/ground volumes to them, and then vice versa, has been the worst move they've ever made, and the higher ups he answers to, have told him that they will be switching back fully to Brown as soon as the shipping contract is up for renegotiating.
There's between 2 to 10 NDA and Internationals left sitting on the rollers in the DLA shipping dept every single day, and sometimes a whole roller line full of grounds - upwards of 30 to 50 parcels on occasion, some are large, expensive overweights, and range from parcels needed by another base asap to extremely urgent supplies and equipment for military operations that could be viewed as a literal life or death delivery.
Some of these packages are NDA to Special Operations Group - classified equipment that must be signed for as you pickup/touch every single package...these packages must be overnighted, and no shipping is allowed on Friday - they are not allowed to sit unattended, while not loaded on a truck in transit, outside of special security clearance government employee/military supervision - when FedEx comes too early and leaves before one of these is processed and ready for signature and pickup, it creates a huge headache for them, and they've got to call higher ups and inform some defense intelligence group, then make an inventory and lock it up somewhere.
Needless to say, they hate FedEx now. They never really paid attention to how bad they were when they were getting the crumbs - but once they were taking the bulk of the pie, DLA found out what terrible service they provided.
We've slowly taken back what appears to be slightly more than half the volume they originally took, despite DLA paying us a higher price than they used to when we had the big dawg contract, and perhaps even fighting or paying some kind of penalty to FedEx for potentially breaking the terms of their current shipping contract with them.
It pays to provide the customer with good service. Smart businesses, and even Uncle Sam, will pay a bit extra on their shipping costs to receive exponentially greater service, and insure the parcels move on the day they're ready to roll, and not at FedEx grounds leisure.