I haven't done the SYD-LAX route for two years on Qantas, but when I did do it (3 times in 3 months) it was just average - nothing great, but nothing bad.
My brother did Virgin PE last year and was very positive about it. Said that he would not consider economy in any plane when it meant "a bit more money" meant that he could do PE.
For my money, Qantas FA's are just average. The planes are okay and it just gets me there.