Upon searching, I found 1-800-drywall to be the most responsive company, and was reasonably priced. As I was unsure about the time-frame of delivery needed, they were prompt to follow up based on our initial discussion. In following up, they were never pushy for me to place the order. Delivery price was reasonable compared to other companies, especially some of the big box stores I contacted, and ordering the product was very simple/user friendly.
The only suggestion I would have is that the delivery staff should make the initiative to be prepared to cover the floors. We had to pretty much make sure it was done - the guys asked if we had anything to cover the floor (even asked if we had any newspaper). Eventually they found some sort of material in the truck, but I found this to be surprising for a company that must regularly walk through finished homes into unfinished basements.
Overall, a good experience, good price, and good communication.