We are long time Celebrity cruisers (8 different ships) starting in 2009. We have also done cruises on Princess, NCL, Carnival and Cunard and were travelling with an older neighbour friend and her married daughter.
My wife and I liked our Deck 11 concierge stateroom. New balcony format adds lots of room and especially for baggage storage when you are packing/unpacking. Window opening does pauses HVAC performance but loss of heat/coolness can be somewhat controlled by closing inner balcony doors. Those inner doors should have vertical curtains so that light could be better controlled and differing sleep / wake up schedules accommodated.
I've been in IT over 40 years and found the internet package coverage was solid throughout most of the ship ship. While we experienced only minor connectivity issues and session disconnects while wandering around the different ship areas, many others were not . Unfortunately many others had Internet speeds on transatlantic crossing were very good with only exception of late day and evening after leaving Bermuda.