My recent USAir flight from EWR to MIA posted in 3 days. My EWR to PHX flight partially posted and I had to send in boarding passes. The portion that posted did not count towards my status and EQMs. A United rep told me the account will be sweeped and it will eventually post. The portion that did post was on former America West.
How and when you get your miles depend on if it is on original USAirways flights or former America West flights.