Granted, I haven't had to return any items so far, so I don't know how they are with returns etc., but I'm satisfied with my experience with them so far.
The furniture I ordered arrived relatively fast (shipping was just $1) and it was the best packed box I've gotten so far. The item quality was great too.
I've since talked to their customer service to ask questions about other items and they were very helpful and informative. I was actually surprised to see so many bad reviews here, so I'm wondering if maybe the customer service at overstock was less good before and I just lucked out by starting to use them after it improved?
In any case, I'm happy with them and had only good experiences so far.