At least Qantas has separate QP and J lounges in the domestic terminal at Perth. I've been in the Perth J lounge a few times this year and I'd say it's far superior to Melbourne's domestic and international J lounges. It's at least triple the size of Melbourne's domestic J lounge (which seems like a disappointing after-thought tucked away in the far corner of the QP) and has a much wider range of food options than Melbourne's international J lounge.I also like the feeling of departing from a proper international terminal, it has got a real buzz to it, whereas an domestic terminal doesn't really excite me.
Anyway I'm willing to try this service at least once to make up my mind, however the main deal breaker is no F lounge and probably a crowded and underwhelming Dom J lounge when compared with a international J lounge .