If you go on the website and click shop now on the rolling ad thing for the discounts those are the only thing you can use them on.. usually it's just cables and stuff. Wish it was for every thing on the site as well.
FYI Shouldn't bother in paying the extra for USPS Priority 2-3 day. My hdmi 2.0 cable I ordered on Saturday had the label printed at 6:48am Sunday morning and it sat on someones desk all day Monday. It didn't hit USPS until Tuesday and should be delivered today. So if you don't mind paying the extra cost from First Class (if your order qualifies that is) to Priority but don't care if you get what you pay for then by all means pay the extra. I paid the extra to get the item by 3 days which "SHOULD" have been Wed when my UN43KU7500 was slated for delivery (It came early on Tuesday) so instead of the 2-3 priority delivery it's going to end up being the 2-5 First Class delivery which isn't what I paid for.
Their CS answer so far (I emailed them again last night so I'm awaiting a response):
Thank you for contacting us, I show on our system the order shipped out as scheduled 5/15. However tracking isn't showing any updates, if you don't receive the order by end of day 5/18 which is the 3rd day from the shipping method selected, you can contact us back for a replacement.
See actual tracking below. Shipped Mon my ass. If it did ship Monday then it's really past on the max 3rd day delivery.