In theory, according to the UA Chart, one can book *A Award trip on united.com. But I always get the following message:

We could not find any additional Saver award seats on our online Star Alliance partners (Continental Airlines, Lufthansa Airlines and US Airways). Please try United award results to search for alternate options or edit search for other dates. You could call United Reservations (1-800-United-1) to explore additional Star Alliance partner options.

Does anyone have luck actually booking on the bomb?