Funguy,
I'll agree with the O&D argument to a point, but PIT has many other things going for it that makes it attractive as a hub. If O&D is to increase, then we have to get involved with local tax structure, which is a whole other can of worms which may be better suited for another thread. At least the traffic choices to the airport locally are improving quickly, so you never know how soon that number might change.
Lemme throw this out there:
Joe Blow is a passenger out of ROA going to ORD. If I'm not mistaken, US flies there from all three hubs. If I'm a (hypothetical) ticketing agent, and available seats on all ORD flights are equal at all three hubs, where am I gonna route Mr. Blow? He doesn't care when he gets there.
CLT? Send someone south to go north? I never understood that logic. Deal with employee shortages at random times during the week? Especially in the winter months? No way!
PHL? Hmm......east to go west? Lost bags? Employees on the ramp who could care less if planes depart on time? Periodic nightmares at the gate if you are unlucky enough to get an agent having a bad day and sharing it with others? No, thank you.
PIT! Go north, young man. The Sunday Night Blues are OVER at PIT. Bags making destinations are the norm, not the exception. Professional employees who do their very best for the passenger. An easy to figure out airport layout.
Now, it may seem over-simplified, but in my experience routing a passenger anywhere other than PIT is a risky proposition. PIT is consistent in doing a good job, and frankly the other two hubs have some catching up to do in the risk category, PHL moreso than CLT.