I have ordered about 50 % of all my Christmas gifts from overstock this year and I didn't have any items canceled. Most of my items were sent in different packages, but they all arrived within a week of ordering through the post office.
My husband in a Rural Mail Carrier so just a little info and rumor....UPS and Fedex both have been known to drop shippments to the post office for the carriers to deliver. What is dropped today will be delivered tomorrow as they (UPS and Fedex) don't drop until early afternoon(at our PO). Rumor has it (in our area) that there were some issues involving fedex and packages were not being delivered to the PO....but were piling up in a warehouse. However, I don't know how true this is.....I do know that a very large shippment (4 Pallets)were dropped, at our small PO yesterday to be delivered.
My personal experience this Christmas was, I ordered from LLBean at the beginning of the month,(order shipped Dec 4 Fedex SmartPost) and I just received it today.
Have faith that if Overstock didn't cancel your order, if the PO recieves your package it will be delivered. They even deliver express packages even on Christmas day.