I haven't been through PHX yet, so can't comment on that.
CLT-As CWS said, big. I find it crowded and on the hot side. It's an easy airport, but I'm not in love with the lounge. Staff are not generous with drink chits for OWE.
BOS-Dark and small, but I find the staff very nice, and I've never seen a crowd.
DCA-The best of the bunch both on staff and overall experience. The old US club is maybe a touch more spacious and better appointed than the legacy Admiral's Club, but you can't go wrong either way. Drink chits flow freely. I'm not a big drinker anymore, but I often stumbled out of there in my mis-spent youth.
