Don't worry.
Just last month I used them between LHR and SYD and I found the flights very nice.
The flight from Vienna to MEL will be operated by a 777. I will be honest and say that the seats are not the most comfortable seats I have ever sat in but they are bearable.
The IFE system is great. Lots of movies, games and maps so you shouldn't get bored easily.
The meals were lovely and I speak for every single onbe of them. they serve warm, fresh bread which is more than can be said for other airlines I have flown.
You shouldn't go thirsty either as the Cabin Crew are always handing out drinks. I lost count of the amount of times they came around.
Overall the Cabin Crew are friendly and helpfull so don't worry about that as I came accross some extremely wonderfull crew onboard those Lauda flights.
If you want an upgrade, I was told that you have to contact Austrian yourself and request it.
I think you will find that your journey will be pleasant.
rehards A340