Right, after almost 9 months and about 1500 miles (in TT bike) I'd say that on reflection it would have been better to bang the star-fangled thing in at the start and then forget about it. Although the bung has worked, it has needed regular repositioning and tightening due to slippage inside the alu steerer tube. I know that in theory the stem should hold the front together when tightened in place, but in reality, once the bung had slipped, a small amount of play started to develop through the headset.
I'm about to build a winter training bike with carbon fork / alu steerer - I'll be using the star nut on this one.