If I were you, I would use those miles to fly First or Business Class on United's new premium transcontinental service from JFK to LAX and back. Many times, US Airways agents don't realize that United requires 60,000 miles for First Class since they have many 3-class aircraft opposed to US Airways 2-class aircraft, so you might end up in First Class. A final note about UnitedFirst on its new premium service, it features lie-flat seats, exactly like the ones offered by Singapore Airlines in Raffles/Business Class (several pictures available at
www.airliners.net).
US Airways is in a very difficult situation, you might want to burn those miles before the end of January 2005.