I know this has been posted before but this is a response to pugsley's question back on 30 June 2011 which has now been closed so could not respond to that.
I applied for MH upgrades to first from SYD to KUL and was successful in receiving them. It was about USD790 each way so cross my fingers for an upgrade on the return leg. It included their service fee of USD5 which is non-refundable if you didn't get the upgrade. The reason why it was charged in USD was that I wanted to use my Amex. So to answer your question to see if you should use them. I would say yes! I guess I got it since there were only 2 other people in a cabin of 8. It all depends on their loading and obviously will not consider if they have sold out/close to selling out the cabin.
Good luck if you decide to go ahead with it!