I'm sticking with this SimpleTech deal and waiting it out. Had good luck with fast supersaver shipping in the past.
Moreover, there's a thread over at Chubby Billfold referencing this deal that contains this interesting quote:
"I remember an item I once bought from Amazon had a rebate that required it to be postmarked soon after purchase too. I called Amazon and the rep said "not to worry, it wouldn't be a problem even if I got the item a little late... just mail it in." I'm not going to bother calling this time, but if the card comes late, I'll write on the rebate submission that "Amazon was late in shipping and the Customer Service Rep stated that this will not be a problem for the rebate." If you're concerned you can call Amazon, but I bet they will just tell you to send it in even if it arrives late and it won't be a problem. "
Another thread over there had this to say about this SimpleTech deal:
"I called the rebate company and they said they would honor 10 days after the SHIP date. She also said if it gets rejected to just call them and they will validate it for you, so you will get the rebate anyways if you follow it and just call them maybe 3-4 weeks after you mail it. "
YMMV, as well may mine.
Update: Mine just shipped. Think I'll be good to go!