WT+ is worth the cash IMO. While the food is of the usual economy standard the exrtra room is quite welcome. On the past 3 out of occasions I have travelled on this class I have been upgraded to J, so there is an extra incentive if you are a punter.
novacatz, definitely worth it. I've used it in the past to SIN, BKK and LHR (from SYD/MEL) as well as LHR/HKG. With the altered QF International upgrade position, QF have almost totally lost me (particularly with better AA earning).
roryg, upgrades are dependent on how many BA Golds, QF Chairmans, QF Plat, BA Silver etc (depending on your status) are onboard as well as you.
I'm running at only 2 upgrades from 6 (and one of those upgrades was my honeymoon).