SA, I wasn't there and I don't have all the information that they did so I refuse to comment on whether or not it was the right thing. I do acknowledge that you can't base the correctness of a decision on it's outcome. Many a correct decision (and execution) has resulted in a less than optimal outcome whilst many crappy decisions have resulted in an outcome that was pretty good.
However, when you evacuate, people get injured. Every major evac of an aircraft in the last bunch of years shows that. When QF banged all the doors out on the 744 at the terminal, we had people injured including a fractured collarbone to one of the crew. In some respects, given the previous history of aircraft and evacs, we're probably lucky there were no worse injuries in Sydney.
With the QF1, they didn't 'sit there' for 20 minutes doing nothing. They spent a lot of that time ensuring that people were briefed for a precautionary disembarkation and then ensured people got off with minimum of fuss and zero injuries.
I wasn't there. I don't have the information that they did and I refuse to judge the decisions that they made on the night regarding evac or precautionary. Based on what I know of our training both before and after, it appears to be a reasonable decision given that I'm not in possession of all the issues that the crew faced. Interestingly, despite their best efforts, neither is the ATSB and certainly no one on PPRUNE.