I still got the impression this year that there were a decent number of first-timers (this was late peak season at the end of August). Obviously though having said that, the ratio is heavily in favour of returning guests which speaks volumes about how successful it is
Merch is still flying by any other theme park standards, but I haven't seen a half-hour queue just to pay in a while. And it's nice to be able to stand in Zonko's without that bell ringing incessantly!