Yes, when you deal with CASA you realise the CAA is not as bad as you thought
You are required to have a security clearance before CASA will issue a licence. This includes converting a foreign licence and validating a foreign licence. I know aberdeen_taffy said he'd managed without an ASIC on a validation in the past but nowadays the first part of validating a foreign licence is the security check. Without that you can't pass GO.
You can get an ASIC, valid for 2 years or an AVID, valid for 5. The big difference is that you need an ASIC to fly into/out of a security-controlled airfield. By this they mean an airfield which has 'regular' (normally commercial) traffic i.e RPT operations. Jandakot used to have RPT but no longer does, so no ASIC required.
I used to have an ASIC but just found paying $250 every two years was a joke because I never go to RPT airfields. They have recently changed the system so that all the documents required (EVERY time you renew) must be checked by a designated person. You used to be able to get the docs certified and submit them (why they didn't just retain and compare them to the existing ones I'll never know) but now you pay the money, they check everything and then you go to your designated person to have the paperwork checked. My nearest person is 2.5 hours drive away. Convenient eh
Small wonder that I thought 'bugger this for a game of soldiers' and haven't bothered to renew it. I've just got an AVID sorted out so at least it lasts for longer.
CASA are THE experts at 'gold plating' and put the CAA to shame. If you don't cross every 'i' and dot every 't' (yes, I know) then your application will be rejected. You'll be lucky if they actually inform you of this. More usually you discover it when you call them to find out what's happening with your licence application.
The really important thing is to think a LONG way ahead if you want to fly in Oz. Converting your licence is sometimes actually easier than validating it and validation only lasts for a maximum of 12 months. That's a lot of nause for a year-long licence
You MUST get your security application in really early because that takes an age in itself and then you can expect CASA to take at least a couple more months processing your application once they've got the security clearance.
Is it all worth it if you're visiting and just want to fly around a bit and look at the scenery? Not really, I'd say. Sure, there are some lovely places to look at from the air and the weather certainly allows a lot more opportunities to take to the air. Equally there is a HUGE amount of nothing, unless you really enjoy rocks, sand and pine trees. I know this can be breathtaking in itself but that soon wears a bit thin. It is great that most places have airfields of one sort or another close by but you're more likely going to be doing the more 'touristy' stuff, so the local town's red-dirt strip isn't going to be much use to you. If you're going to tour the whole country by air that is one thing and is certainly worth doing BUT if you're here for a month or so and want to see the place by air you'd be better off just going to local aero club and going up with an instructor in the right seat or taking one of the tourist flights if you're in an area that warrants it. Yes, these are costly but I reckon it'll work out a LOT cheaper than doing it yourself and a HUGE amount less bureaucracy.
Having said all that, it's a beautiful day outside (even though it's winter) and now the sun's up I think it is time to go and turn upside-down. Well, somebody has to do it