I order from CSN/Strollers.com all the time. Their returned seats 90% of the time haven't even been opened... people ordered them and then received the box and changed their mind. About 10% of the time they have been opened and looked at and placed back in the box. MOST of them havent even been removed from the plastic and the boxes come in great shape with CSN tape on them. So in my opinion you are getting a heck of a deal on a seat that you can OBVIOUSLY tell hasnt been used if it's still in plastic and has all tags attached
I have ordered several seats from them and have had the same experience. Tags still attached so obviously not been used.