Last year one was able to earn status miles (i.e. Preferred Miles) on US Airways and also receive bonus miles based on your status and based on fare class. All business class fares also resulted in the 150% business class bonus.
This year one can only earn regular miles, bonus was reduced to 125% for C,D,J business class fares, Z class fares have no bonus, and no status bonus.
This is rather disappointing though what is probably the most inconvenient is that there will not be a baggage interline agreement with United after September but there will be with American and JetBlue (where there is no mileage partnership).
It hasn't been explicitly stated in this thread, so to prevent someone making a mistake based on outdated information:
Discontinuation of United Airlines Partnership
Effective 14th September 2012, United Airlines will no longer be our Airline Partner.Therefore, Privilege Club members will not be able to earn Qmiles nor request an award ticket on United Airlines after 14th September 2012.
This applies equally the other way round. You can no longer earn Mileage Plus miles on Qatar Airways effective September 14, 2012.