I was able to successfully verbally declare an exemption at an Apple store in August, although I had to do so three or four times over the course of the transaction as I was passed between staff members.
I've seen a number of people on Twitter complaining about having less success. Indeed, this is the first case I've heard of where they have accepted exemptions - well done

(Personally I haven't tried - I find Apple stores irritating at the best of times).