Never had issues in the domestic terminals (T2 and T3). Both are very easy to use and get around with plenty of facilities and lounges to keep one busy should there be a flight delay (given how busy it gets there is potential for this to occur). In particular the food court in T2 (Virgin Blue Jetstar and regional NSW flights) has a great range of outlets with good views of planes moving around. For aircraft aficionados there are plenty of spots throughout this terminal for viewing planes taking off and landing. T3 is pleasant and is open throughout. It's easy to travel through yet doesn't have the same range of shops as T2. Staff are friendly and there is an interesting Qantas Heritage Museum located near Gate 14. Transfers between these terminals is easy through a subway that also goes to the railway station. T1 the international terminal has just been refurbished and is rather pleasant with a large range of shops to rival other airports worldwide. Going through customs etc. to leave the country is often a speedy process with queues minimal. However re-entering the country is a lot more difficult with queues for customs taking a while baggage taking its time to arrive on the carousel and immigration taking a while to screen everyone and their respective goods. I understand that they're trying to be scrupulous with who and what to allow in the country but surely there must be some way to speed up the process. A word of advice is to not arrive on a flight between 5am and 9am when most large long-haul aircraft arrive meaning particularly long queues for all arriving passengers. In general however it's an easy airport to use with all facilities that one could need. I've never had to transfer between domestic and international services although I wouldn't imagine it would be an easy task.