I have been avoiding this thread and I have not read all of the pages and pages of responses, but I think it is time to comment.
Doug Nancarrow is a well respected aviation journalist and has been for many, many years. I'm surprised people on this forum don't know of him. I can't imagine he would ever have wanted to inspire such a divisive response.
Now on to the subject. No one likes to be criticised but let's be realistic. RA-Aus is the less expensive alternative, and there are reasons for that. The training standards are different. Now that doesn't mean that all RA-Aus students receive minimum training, but some would. It doesn't mean that all RA-Aus instructors have very little experience, but some do. It doesn't mean that all RA-Aus pilots don't have the theoretical knowledge to pass GA exams, but some don't.
Some RA-Aus aircraft may be more difficult to fly than some GA aircraft, but some GA aircraft are way more difficult than some RA-Aus aircraft too. Some RA-Aus aircraft may not be maintained to GA standards, but some are immaculate!
RA-Aus can't have it all. It is not possible for all RA-Aus students to receive the same level and extent of training as GA pilots at a fraction of the price. Some might receive a similar level of basic training if they are fortunate with the school and instructor, but you can't count on it, and it is simply not possible to do the "extras" without GA training.
Every single GA pilot has been trained by a GA commercial pilot, who has passed all those exams and flight requirements, then passed an instructor course of a minimum of 50 hours at the very least. Yes, some RA-Aus instructors are skilled pilots with great teaching skills and some have vast experience - many in GA, commercial charter, flying in the airlines and military - but some are not.
Every GA PPL has received some instrument training and can fly in Class C and D airspace. GA pilots have the option of training in aerobatics, night flying and completing a 40 hour instrument rating, and many do. All of them hold an aviation medical. The flying schools must go through the procedure of getting a CASA AOC with significant money and time required.
As Ian has said, there are good RA-Aus and GA pilots, and not so good pilots in RA-Aus and GA.
It's too easy to point the finger quoting a single incident, but all of us make mistakes. Those who deny having made a mistake are either very inexperienced, or kidding themselves.
On the IFR issue, one thing to consider is that IFR GA pilots preparing for an approach have a pretty high workload and would be talking to ATS because they require traffic information and are on full SAR reporting, then transferring to the CTAF and self-separating from IFR and VFR traffic there, and flying an approach where only 5 degrees off track means they cannot continue. If using multiple radios (while talking to ATS and monitoring a CTAF for instance) it is very easy to transmit on an incorrect frequency. An IFR radio call might mention turning inbound on the NDB approach, but of course it is better airmanship to say turning inbound on the NDB approach x miles north west of wherever at x feet so VFR traffic can maintain situational awareness.
I'm a huge fan of RA-Aus, but please don't start attacking GA. There are so few pilots in Australia anyway, a house divided against itself cannot stand. We all love to fly and are required to comply with the rules of the air.
Let's work together and share the air, not attack each other without good reason.