So despite also having separate domestic and international terminals, Brisbane has actually got its shit together.
There’s a train that runs between the terminals roughly every 10-15 minutes. Which is free if you have your onward boarding pass. Otherwise it’s about AU$3 or something each way. It’s about a 2 minute train ride and drops you right outside either terminal. There’s no big hike to get anywhere, just a couple of elevators. If you’re heading to/from the airport from/to the city, then there’s a train that goes right in to the CBD. One way ticket is like $12. I’d do this rather than get a taxi, which can be insanely expensive. You can always just get off the train in the city and catch a taxi from there. Will work out much cheaper. The trains from the airport also go directly to the Gold Coast if that’s your destination. Not every train does, but I think they run every 90 minutes down the coast. Also a much cheaper alternative!
International check-in is also pretty smooth. At times I’ve had to fly on under 24 hours notice, so the customer service desk there holds on to your tickets for you since the airlines won’t issue e-tickets less than 72 hours before flying. They’re great 
There’s plenty of seating once you clear security. And security is maybe the only downside I guess at Brisbane. It’s a relatively busy airport for its size. But they never seem to have enough staff at customs/immigration. Either on the way in or on the way out. The lines to pass security to the departure area are always long and painful. The lines at immigration on the way back in to Australia are always painful, even if you’re travelling on an Australian passport and worse if you’re not. Quarantine seems to move relatively quickly though which is good.
For the non-Aussies, clearing quarantine is compulsory in Australia. Unlike many countries where you just go through the “I have nothing to declare” lane, here you have to go through quarantine screening. Even if you have nothing to declare, your bags will still get screened after you pick them up so that they can make sure you’re not bullshitting them. And don’t lie to the quarantine people! If you have wood carvings, just admit it. It’s not illegal to have them, you just need to declare it. Worst case scenario if you declare them is that they’ll take them off you for spraying and you can collect them a few days later. If you don’t declare them and you get caught, it’s an on the spot fine upwards of $220. I’ve seen too many idiots lie to quarantine about having certain items. I’ve brought in wood stuff and food when I come back. I’m a sucker for certain foods I can pick up duty free in Singapore at the airport. But I declare it, the quarantine people look at it and smile and let me keep it and that’s the end of that. I’ve never had anything confiscated. That little arrival card that you fill out when you’re on the plane to Australia is important. Seriously, don’t lie. It’s more trouble than it’s worth.
Shopping there is a bit average. But also, it beats Perth hands down. There’s plenty of food outlets. There’s a much larger range of duty free booze/electronics/beauty stuff. It sells duty free luxury goods, even if the range is limited, it’s still there.
The airport lounge for Qantas is quite nice and you get a good view over the departure area. It’s not a bad place to lounge when you have a 6 hour layover. Hey, we all try to avoid long layovers, but sometimes it’s impossible 
Overall, while Brisbane has a small international terminal in comparison to many others around the globe, it’s a good airport. It works well and it’s not an airport that I’d try to avoid travelling through in the future.
