Most reviews seem to be Coral class, and people seem quite happy. I have flown 4 long haul legs in Diamond and I can honestly say Etihad is the worst I have ever experienced for a first class seat.
The chair comprises of a 1 inch foam sheet with cloth cover, which is attached to a metal frame via velcro. But you can feel the bolts etc under your legs. I am sure the Coral seats must be nicer(from the reviews).
The flight lounge at Abu Dhabi(which is their HQ) has mouldy, dirty showers. The food consists of frozen bread rolls and pastries, plus a few other types of muck, and is completed by a train-station style vending machine for coffee. Absolutely foul.
The inflight entertainment is clunky and did not change over 2-3 weeks. On every flight, 1 or 2 people in Diamond class has problems with the chairs getting stuck. For example, on my last flight 4 attendents were trying to get a passenger’s chair to recline to flatbed.
I think the answer for first class passengers is: never fly with Etihad. I certainly won’t use them again.