Most the US Airways flights are out of Concourses B&C and United is out of D. It is an easy connection and you do not have to go through security. There is a moving walkway between C and D (the RCC is in that corridor as well.) Shouldn't take more than 5-10 minutes to get between any two gates.

RCC there is pretty worn, although the ladies at the front desk have saved me on countless occasions!