The lines here at RDU are variable. Usually not too bad, but once in while it backs up at the "main" checkpoint near the USAirways escalators. The suggestion to go down to the entrance by Southwest is good. And, since many USAirways flights actually leave from gates near Southwest, it is likely you would have to walk that far anyway, even if you went through the main security checkpoints. (So you are not adding much, if any, extra walking time by going to the Southwest checkpoint).