I purchased an Antminer S1 on 4/9/14 and sent Bitmain an email asking if I would get a coupon and they said that "yes, coupons will be ready soon".
So I'm confident that I'll be getting a coupon soon.
So far every time I sent an email to them they've answer me within a few hours.
What email address did you use? I just PM'ed them here on the forum but wanted to send an email too.