I posted the following on another thread which I thought might be of interest to all FlyerTalkers. The system has been workiing for me for the past year about 85-90% of the time:

If I book a flight through a Star Alliance Partner, I always use Destina. The seats are automatically assigned following which I phone destina within a day or two and request a change of seats to the Y-Plus section. It worked for me throughout all of 2003 with the exception of LAX-HON-LAX.

Naturally I keep tables of the seating allocations for UA's fleet of aircraft so I know what rows to ask for.

For those who dislike Destina simply because it's run by AC, swallow your pride and go for the extra leg room!

BTW, I've also found that having a BP for Y-Plus increases your chances of getting upgraded to the front of the plane.