My wife and I recently flew from Melbourne to Narita and return on Jetstar. Here is a list of our bad experiences with JetStar:
1. We booked the flights through Qantas Frequent Flyer with points. Our itinerary had a Qantas booking reference which could not be used to check in on the Jetstar web site which requires a Jetstar booking reference. We couldn't find a customer service phone number on the Jetstar web site and the online chat facility proved useless at solving the problem. Eventually my wife found a contact number that someone had posted on the internet so I rang this number and spoke to someone in Asia. They eventually gave me a Jetstar booking reference and I was able to check in online. I wasted a lot of time on this.
2. We wanted to book meals on the flight but attempts to do this online failed for some reason. I rang the secret Jetstar customer service number and after half an hour or so of conversation was able to book the meals. The service person said that they would send me a confirmation email but it never arrived, and the Jetstar website was showing no meal bookings. I rang back to confirm that the meals had actually been booked and received verbal confirmation. Again, wasted a lot of time.
3. We were on the train to Narita for our flight home to Melbourne and noticed on the in-train flight information that our flight was scheduled for "tomorrow". When we arrived at the airport we learned that the flight had been cancelled. I did not receive any email or text message telling me that the flight had been cancelled, and the cancellation never appeared on the Jetstar website. While waiting in the queue at the Jetstar desk we rang Qantas and arranged to board a Qantas flight leaving at about the same time as the Jetstar flight, for a few extra points. The other unfortunate Jetstar passengers were being shunted off to a hotel for the night. I should mention here that we flew to London on Air Brunei in December, and they cancelled the flight but put us on a Qantas flight leaving at a similar time. I'm not sure why Jetstar couldn't have bumped us across to the Qantas flight leaving at the same time, especially as the Qantas flight was only 2/3 full.
4. Using Qantas FF points, the fixed charges and taxes were approximately half of the cost of the full Jetstar return fare, and that's without booking any extras such as seats, meals or entertainment.
Conclusion: Completely bad experience with Jetstar on all accounts. You can book an equivalent flight with Qantas (no stops versus Jetstar stop at Gold Coast) for a few extra points and avoid all the problems. Never again Jetstar.