I find that I have to be pretty proactive to achieve the fix times.
RTA in my machine works but does things that would work ok in a sim but in real life is a case of the machine over estimating its ability to handle turbulence and big wind changes. The speed bug sitting suddenly on MMo and then 1 knot above up/green dot speed is an example of RTA in my machine.
Personally I opt to not criticise as I don't have the full picture. I can say however a controller palming me to another frequency for further descent as I'm about to capture an altitude at high speed is very very annoying and is very uncomfortable for everyone on board. It seems also enroute to Perth from the east coast that the clearance seems to arrive a bit later than it should and we end up all arms and legs when its not what we expect.
Other than that I've accepted that when you fly along the east coast expect the worst.
One other thing. Max speed into say Gold Coast or Launceston doesn't work for Jets as the profile will bust just about every CTA step there is so why give it? Send us on a vector rather than put the workload to that level..