I found them to be professional. Not exactly Amazon but who is... I purchased a new Sherwood R-972 from them. The first was defective (wouldn't find the speakers during EQing 100% of the time) and I had to return it directly to Sherwood on their dime before they would ship a replacement. I got tired of waiting for the return label and ended up purchasing another and they refunded my money on the original unit. The second unit would report incorrect data for the speakers during EQing (quite often but not always) and it scared me enough I punted and returned that one as well. Since I wasn't going to try another the return shipping was on me which I knew going in. After a few days they refunded me the cost of that receiver and didn't dock anything for the free shipping.
Regarding their refurbs personally, I find Fry's on certain models will beat them at times. Other places will as well... although you might not have as a large of a selection and Marantz is hard to find discounted. Best Buy (Magnolia) is pretty good for Marantz close-outs. I purchased a SR6005 and SR5006 (brand new) there at a killer price. Recently, they had the SR6006 for $549 (new) although finding one in stock was tricky.