Great that you have got your S3 you lucky chap!
Re: handbrake what is the main niggle with the electro brake? I am wondering if it was something that the hold assist option would have resolved? Lots of people posted some initial issues with their A3 electro h/brake so perhaps its just a matter of getting used to it?
I have had hold assist option on 3 other Audis, A5 x2 and A7 and it is I think a great option. In traffic just flick in on, all issues solved. Should be standard (it is on A7) on all cars with electro brake.. just Audi being mean !!