We flew LTN EWR 20 and 21 Dec and returned on 3 Jan. Paid £1700 for two and it was well worth it. We booked late and could get nothing from Manchester for that price in economy even going via Istanbul or spending 13 hr in Dublin.
Everything worked well in LTN and lounge was a welcome refuge from a very busy airport. Flights were quiet (34 on 20th and 24 on 21st). Food choice was fine although they'd changed menu from website and had we know new choices we'd have ordered vegetarian for our teenage daughter. Some seats wouldn't adjust but they were sorted manually and there were enough spare seats to move. Luggage was quick to be delivered.
Car rental return at EWR is much easier than at JGK. Xheck in very quick and easy. Lounge in EWR is landside and is too small with poor food that ran out and they didn't tell us it was time to board which meant we were very last to board. Weren't even properly seated when flight left 15 mins early. Didn't eat as I just slept. Bed wasn't that comfy (bit hard) but did manage to sleep. Flight arrived early and luton at that time is quiet so we were on the motorway within an hour of landing.
A few niggles but all in all I would definitely recommend them amd use them again.