I have just come back from a trip which took me to 5 different US airports. Only two had an Admiral's Club. The one we were able to use was basically the same level as QC Domestic but needed our drink voucher, no computer access, but they did allow us to bring in food from the food court downstairs (even though there were signs saying you couldn't). I believe that was in Dallas, Fort Worth. The other airport which had a club listed 2 different lounges but the one near our gate was closed down (no signs to tell us that until we got to it of course!). No other airport had a club and some didn't have dedicated check in for Admiral's Club (which QC can use) or One World.
That said, we used the Admiral's Club at London, Heathrow as BA didn't have a lounge in our terminal. We found it to be the best of any lounge (apart from the swanky new QC in Singapore - pity about the lack of air con though...). The bar was self serve, no vouchers required, and the bonus was a special area which was a quiet zone with leather recliners. As my fiance had a migraine (not good before a 9 hour flight..) it was an absolute god send. The downside was that the other areas of the lounge were playing the royal wedding :roll:
The combined BA/QC at London Gatwick isn't too bad - it is multi level. The BA lounge in Venice was nice - I savoured my last real cappuccino which was actually made for me, rather than the self-serve QC machines. Be warned though, the person on the desk didn't want to accept my QC card - thought it was bronze FF but I insisted and she called BA to confirm.
As for the worst lounge - that absolutely has to go to the JAL lounge at Tom Bradley in LAX which is the one you will have to use if you fly out of that terminal. What a joke! It was absolutely tiny, no phones, no computers, no toilets in the lounge!! Food was chips or some stale rolls in the fridge (or for the very brave, some American "cheese"), but at least the drinks were all free. We were told that the new QC lounge in Terminal 4 was much nicer but weren't prepared for that. Next time we will go via Sydney. Didn't have a choice this time as we had upgraded on points. Alas, all about to end soon..... :evil: