We just traveled on Jetstar, Melbourne to Honolulu for our Aulani trip in November. (LOOVE Aulani BTW)
The flight was comfortable, nothing amazing. I've had worse. It got us from A to B, and that was the main thing. Crew were nice, the food was meh, but no more meh than other airlines. It wasn't worth paying extra money to fly with Qantas. We went for the Jetstar bundle that gave us checked baggage, meal and Qantas FF points. Worked out cheaper than buying them separately. If you think you may want a meal, select the bundle when you book. There were people who didn't book a meal who missed out. Also, it's cheaper to add checked baggage when you first book than it is to add it later. This is also the case if you want to add extra kgs. (eg from 20kg to 30kg etc).
Overall the flight was pleasant enough. We got return fares for about $750. Qantas and Hawaiian were charging over $1000. I'd fly with them again if the price was cheaper than the other airlines, but I might consider taking my own food to eat, particularly for the flight home. The breakfast burrito (provided by their US caterers) was not great. There are places in the airport where you could have bought better quality food to take on board.
No real inflight entertaining unless you want to rent an iPad. Take your own pre loaded iPad and you are set. I always prefer watching things on my iPad vs a back of seat screen, because the quality is so much better.
Jetstar is the easiest way to get to HNL from Melbourne, so I'd fly them again.