As a self funded flyer, mainly to Europe and Asia, JETSTAR can be very useful. I have flown to SIN and PEK several times on JQ in Business Max. Main reason it is about half the price of QF business and you get ff points and SC as per QF. With the new "enhancement" it is in fact even better as you get the "old" SC without all the new levels. I have booked a return trip MEL to BKK in JQ Business Max and on with AY to HEL and LHR all in business for $1650 on JQ (QF $2800)and AY $2900. Gives me a total of 600 SC! QF in PE would be about $5500 and I certainly would not get that many SC in PE on QF.
JQ in business is not the same as QF international, (almost exactly the same as QF domestic business). But at roughly half price and full status credits it is worth it in my situation. The staff in the JQ business cabin are no where near as good as QF cabin staff, but they are helpful and try hard. I suppose you get what you pay for. I look forward to trying AY business, particularly, their new cabin.
It would not suit business travellers as it takes much longer than QF/EK MEL to LHR, so it is not for everyone, but can be a very good alternative.
Having said all this I don't fly JQ domestically.