Yep, it's good advice, in a general rule-of-thumb, make-it-easy-for-the-punters-to-understand way (
they made one for us rocket guys, too). You can find out the boundaries of controlled airspace by grabbing a Visual Terminal Chart (VTC) from Air Services Australia. It's a great $10 investment for those of us that like to poke things into the air without being part of a club.
https://www.airservicesaustralia.com/store/html.asp?/bookweb/catalog.cgi?stype=c&stext=VTIn a nutshell, controlled airspace has different classes that you can think of as layers. Here's a guide that explains it a bit.
https://www.airservicesaustralia.com/store/html.asp?/bookweb/catalog.cgi?stype=c&stext=VTThe layers are usually designated by a lower limit (LL on the VTC). Basically, they start at the airport with the LL of the surface (SFC). They radiate outwards, with the LL lifting in a series of steps, in a sort-of upside-down cone shape. The airspace underneath the steps is not controlled airspace, and you can fly in it. Obviously, you'd avoid designated corridors and such. For example, from the Cairns Airport, if I head towards the south west, the steps go from C LL SFC (ie class C, Lower Limit Surface), to C LL 3500 (ie 3500'), to C LL 4500, to C LL 6500, to C LL 8500, to C LL FL125. This last one is nearly 150kms from the airport. These aren't concentric rings either, so it's worth having the chart.
Hopefully I'm not teaching you guys to suck eggs. I just hate that folks think they're restricted to 400' AGL, when with a little extra knowledge, the sky is the limit.