You have to use a9 "regularly." I don't know what that means, but that's the rule. I don't really use it at all, so I don't get the discount. It was nice back in the day when you just had to have used it once.
I used it for about two weeks before my Amazon front page said I was eligible for the discount. Its only 1.57 percent, you would have to spend several hundred dollars to see any savings. Thats only $1.57 on every $100 you spend.
Alright guys...i've been using it every day since the OP (June 26) and I now have the 1.57% discount (3 days later)...thanks for the rough estimates guys (Now time to buy!)