I picked up the 24-70 II. It is interesting that you have to read the rebate carefully. You have to pre-submit online and enter the serial number and then print out a form to submit with the SKU barcode from the end of the box. They insist you cut the label off attached to the cardboard.
You don't have to pre-submit online, that is just an option that makes it easier.
But, you do have to cut out the UPC on the box making a hole in the side of the box. This is done to prevent you from submitting for the rebate (which will get you the rebate money) then returning the lens. By cutting a hole in the box you can't return it.
It makes sense if you think about it, as I am sure there would be people scamming the system if they could.