I've received several packages earlier than expected from UPS, both here and at my office. We also had this happen a lot when I used to summer student work in the mail/shipping center for a big corporation here in Birmingham. And like somebody said above, UPS usually tries to be VERY accommodating to their business customers. We've had fantastic customer service from them in the past.
However, I've never received a package early from FedEx. Granted, the vast majority of FedEx stuff is overnight and for that service they simply can't be beat. They have an amazing track record. Out of hundreds of overnights I can only remember 2 that were late. However, on 2-day and their slower services on almost every occassion the package will arrive in town very quickly and then proceed to sit. I realize if you didn't pay for the quicker overnight service you therefore shouldn't expect quicker delivery. But with online tracking allowing you to see where your package is, it can be very frustrating sometimes since I know for a fact that some of those trucks go out with room to spare on some days. If I really need overnight service I gladly pay for it, but it's always nice whenever a business is able to give a customer a little added value. It keeps people coming back. That's why I now use FedEx for overnights only and UPS on everything else.