I am a comparative shopper and I often check several sites simultaneously for the best deal before purchasing online. Overstock wins so often on price for the exact items I want that I joined their affinity program to get their rewards.
I find that their search function and item descriptions work better than some of their primary competitors. Overstock seems to the fact that it is important to have precisely consistent item descriptions, so that users can search successfully.
In the event that something isn't as wonderful as what it was supposed to be (it is so hard to know when buying online), customer service makes it right. You may have to voice your displeasure in order to get them to make it work out okay for you; but in my experience they will make it right.
I called to cancel an order once, when I had forgotten to link from an email so that a % discount coupon would apply, and the customer service rep offered to go into the order and apply the coupon. That's perfect customer service in my book.
Some parsons chairs that I ordered arrived with upholstery that was so papery and flimsy that it would not have lasted a year. I felt that they should cover the shipping back, as I was only returning them due to the unexpectedly low quality of the fabric. After some discussion of the problem, the rep saw it my way and Overstock covered the return shipping.
A Fossil watch that I bought WITH the Jewelry Protection option, lost its second hand within the first three weeks, and needed a quick repair to put it back in place. The first rep that I spoke to in the Jewelry Protection area said that it was still within the time period that required me to go through the manufacturer to get it fixed. I spoke to her supervisor and quoted from the jewelry protection information where it said they would cover it immediately starting at the time of purchase. He agreed with me, and said that they would take care of getting it replaced or repaired. The watch was no longer available, so they couldn't replace it and had to repair it. They supplied a shipping label, repaired the watch, and shipped it back. It has worked perfectly ever since.
I bought a rug, which was drop-shipped from the manufacturer, and it arrived with some glue spots on the front from the manufacturing plant in China. I called Overstock; they provided the return shipping label, and they had a second rug shipped out to me immediately, before I shipped the first one back. The second one is perfect. When they received the first one, they communicated very well via email, advising that they had received the first one back and had already shipped the second one.
Between their people and their systems, I give Overstock a full five stars.