I've bought a couple of items through warehouse deals, a Garmin 200 (which is still going strong a couple of years later) and a 2nd generation Kindle.
Both were meant to be 'refurbished' to be as new with some cosmetic marks but as far as I could see they were both brand new, the packaging didn't even look as though it had been opened ... maybe I got lucky and they sent me new as they had run out of refurbished items.
After a few months I noticed on the Kindle tiny cracks in the front bezel, they didn't stop the unit from working or anything but thought I'd try it on with Amazon anyway and to their credit they replaced the refurbed unit with a new one without any arguments.
I've not had any problems with the Garmin so far, but going on past experience if I was looking for a new GPS I'd certainly consider warehouse deals if the price was right.