Quick report on my lounge experiences, as promised:
PRG: was flying on TAP and received an invite to the contract lounge at check-in. After passing though security, turn right and take the elevator on your right. The lounge was small, but not too crowded. Small room with 3 computers, larger sitting area and food/bar area with long counter and barstools for seating. I was there in the late morning, and there was a decent snack selection (breakfast pastries and chips) and to the delight of my partner, a nice selection of Knorr powdered soups. Standard drink selection and the wine is served in small individual serving bottles, so you can always snag one or two for later on in your hotel room.
The lounge seemed very modern, clean and bright. Free wifi available.
BUD: The contract lounge is small, but I was there in the evening (6PM) and although the airport was totally packed with holiday travelers (not an empty seat to be seen) the lounge was almost empty. Very limited food selection, but good selection of drinks. The free wifi was not working, but it seemed to be an airport -wide issue, not just in the lounge.
WAW: I was in the airport twice, but was refused entry into any lounge the first time because my LOT flight had been canceled and I was rebooked on Czech air in economy, so a Skyteam boarding pass with a *G card did not work.
The second time, I was flying business on LOT and got into the Ballada lounge no problem. This was very early in the morning and so the lounge was not crowded. Very poor food selection, but good drink selection and also free wifi (get password from agent). The lounge was small, but clean, and as previously reported, no windows.
The lounge in PRG was without a doubt the best of the three I visited.