GPU's as you have discovered are a great marketing promise that looks good on paper. Using them for some of us can be very frustrating if we want a GPU to be confirmed at time of booking. It would not be so bad if buying an eligible fare did not involve a game of chance such as this lottery. For me this is one of several reasons I"m not working to re-qualify as a 1K again this year. In fact this GPU aspect often leaves me feeling so angry that if I can't confirm something at time of booking I refuse to book the trip on UA at all. My revenue immediately goes to another carrier as a form of protest.