I've flown QF Y+ a couple of times on the clients' dime (only seats available) and in all honesty, it wasn't a particularly awe-inspiring experience; so much so that I certainly wouldn't bother forking out the extra $$$ for Y+. Business I can certainly see the value, but Y+ over Y no? IMHO not worth it - YMMV.
Personally I'm the complete opposite. If I'm paying, Y+ over Y is fairly easy to justify, but J over Y (or even over Y+) is nearly impossible. Happy to sacrifice points to upgrade from Y+ to J, but not pay another 2x as much on top of the 2x already for the Y+ ticket over Y. That kind of money can easily represent another couple of weeks accommodation on holiday.
Every flight I've ever been on with Y+, it's been wall to wall, and I've also missed out on points upgrade requests to Y+ several times (presumably due to it being full of revenue passengers).
IMHO the only good value J flying is a (not-ex-Australia) DONEx.