I've been upgraded 12 of the last 13 flights I have made on CX since July (most long haul).

I always fly in J, but I don't always buy J, I study the loading using http://www.flyaow.com/classavailability.htm . Where the flight is full or oversold in Y, but empy in J (J9C9D9I9) you can be pretty much guarenteed a free opup form Y to J. Free opups is like money in the bank! Especially if your buying your own airfare (not company paid)

This is often the case on the summertime runs to LAX & back.