I'm not as nearly experienced as most others here, so I'm always very impressed by (the staff at) Changi.
From arrival, having trolleys available almost at the plane's door, through immigration and customs, and luggage pick-up, to departure and the check-in staff, customs and immigration on the way out, and trolleys everywhere. Clear signage, and people polite and helpful (and usually smiling). The whole process, coming in or going out, is done within 30 minutes, at a steady, but not overly-fast, pace. And the facilities provided for passengers are excellent.
Compare that with Sydney where trolleys seem an impossible dream, the staff (airport, airline, customs, immigration) all seem to be, well, suspicious and even jealous (that you've been overseas, and they haven't), and it takes hours.
As said earlier in this thread, Sydney could learn a lot from Changi.