I completed two orders just a couple days ago. It did take a couple days to ship, then a couple days after receipt to process. They do need to be complete and in good shape.
At least for mine, I was able to pick UPS or USPS shipping.
My trade in order was submitted 11/28, I don't think I shipped them till 12/4, and I got the credits a couple days ago. So, about a week?
My biggest concern is that the trade in values change very rapidly - sometimes multiple times in a day -in fact I created the same trade in orders about five times till I thought I was at the peak of the trade in prices [I was pretty close].
No real complaints. I'd almost rather take the hit up front, in lower trade in values, with free shipping; than pay Amazon's rapacious Marketplace commissions. Plus the bastards cancelled my Seller account, as far as I can tell, because I didn't have enough volume.
Like any trade-in, you will probably do better selling to a person, but it's so much easier selling to a vendor.