I recently took a flight from South Carolina to Maine on US Airways. My experience was fine overall. My main concern was the fact that neither of the planes I took (from Charleston to Philadelphia, then Philadelphia to Portland) offered plane-side checking of larger carry-on bags. Fortunately my carry-on suitcase just barely fit in the overhead compartment, but if I'd found that it hadn't, I would have been in a bind!
I'm not sure why US Airways is limiting plane-side checking. Keep in mind that this might be the case when you book your flight with US Airways.