I went to Australia 10-12 yrs ago. Flew from NC to Hawaii, spent the night, then Hawaii to Sydney which was the longest leg. On way back flew from Sydney to LA.
We flew on Qantas of course but upgraded to business class which ended up being the best investment ever. We basically had our own 'pods' which would recline to almost flat, ALMOST flat. There was a curtain you could slide over when sleeping or want privacy. I watched TV and movies the whole way there and back, They would gently wake you up when it was time to eat, it was way better than I expected cause I was really nervous being in the air that amount of time and having adequate leg room (I'm 6'4")
Coach was in the back area so i really didn't see what those seats were like but Qantas is an awesome airline, I'm sure if you are sitting in coach it will still be comfortable in some way