If you can get MFU-able seats, then it is not a bad use of miles per se. However, these seats are tricky to get. One problem is that you need to book a full year in advance to ensure there are business class seats available for the upgrade, but you are unlikely to find cheap WT+ seats on sale until closer to departure.

In general, using miles to Oz is poor value because business class fares to Oz are relatively cheap if you use cash and relatively expensive if you use miles.

Assuming I wanted to travel to SYD between 2-16 October 2006 in J, Expedia can sell me a business class ticket on China Eastern for £1,320 plus taxes. It would cost you 200,000 BA Miles for the same ticket (albeit with a better seat) - a truly pathetic 0.66p per mile of value.

(In fact, it could be even worse - Trailfinders will sell you the China Eastern business class ticket for just £1,230 INC taxes, so probably sub £1k before tax, as long as two people travel together.)

In comparison, the cheapest business class flight to San Francisco on the same dates (1 stop on the way, flying Continental) is £2,225 plus tax. On BA this would be 100k miles, so you are getting 2.2p per mile of value.