When I checked in at EWR for the Cathay Pacific flight in business class to Hong Kong, the agent told me that the British Airways Galleries lounge was available for Cathay premium cabin passengers and OneWorld Emeralds and Sapphires.
The Galleries lounge is after security and just before reaching the duty free sales area for gates 50 -58.
The Galleries lounge is a medium sized lounge 760 square meters. On the night I was there it was practically empty. While there were no British Airways flights at that time, the flight to Hong Kong had 40 business class seats (about 2/3s occupied) and there were probably additional passengers who had access to the lounge through OneWorld elite status.
When you enter the lounge there is a small seating area directly ahead.
This area has a small buffet of soup, salad and cold sandwiches.
To the right of the first seating area is the British Airways first class dinning area. It was closed since there were no British Airways flights at that time.
Beverages and additional snacks are behind the first seating area.
The main seating areas are behind the beverage and snack section. The seats are comfortable. There is a view of the tarmac. Electrical outlets, however, are not plentiful.
To the right of the lounge entrance are the bathrooms and showers. I peeked in a shower room just to see what it looked like.
Other than slight disappointment with the food options, my experience in the Galleries lounge was completely satisfactory. It was nice that the staff asked on a couple of occasions if there was anything I needed, and they were apologetic about the food situation. As is apparent from the pictures, the lounge on this night was neat as a pin. I would expect though that this lounge might get crowded and the appearance might not be so impressive when British Airways flights are departing.