I am not the OP, but I think two of the best hubs in the US are (unfortunately for UA frequent flyers) non-UA hubs: MSP and DTW (NWA's World Gateway terminal, not the dumpy Smith terminal used by UA).
Having recently flown thru these airports on NW after a canceled flight on UA, I can say that DTW was an excellent experience. ^ A bit like a cross between DEN and ORD. MSP is a an "eh" airport for me. No big whoop. The UA concourse is usually crowded and dark, but it seems like most carriers save their best concourse design for their hubs (except for UA/IAD
).