the F-22 is still quite maneuverable, not to mention it can cruise at mach 1.5 (without afterburners)
in simulations against SU-27's, the F-22's just ate them for breakfast. the SU-27's could cobra all they like, but the F-22 only had to turn around, aim and fire.
but yeah, being stealth is probabbly its biggest advantage
but they are the most expensive fighter in the world (which is most likely why Australia aren't getting them)
$350 million US each, compared to the F-35 which is about $60 million US each