I just flew on this today the result of some irrops and really lucked out. There are 2 77Ws inbound from JFK: the AA100 and 106, the former at 1815 or so and the 106 is at 1940.
I echo the OP, this plane knocks spots off of BA in the round. As a frequent NYC flyer let me give some +/-.
The AA lounge is so so but adequate, prefer BA.
The plane - excellent. I was in J and its very Cathay Pacific, layout is 121 and whilst on first impressions it looks like a huge dorm, the seats are very private, you cant see anyone. Huge TV and bose noise cancel headsets- loads of AVOD just like CX, why oh why BA cant have 100s of choices like here. Plenty of cubby holes like the OP mentioned, very airy and spacious. Seat easy to control, good sized table and lots of shelf along window.
Joy of joys 2 individual air nozzle things that actually worked and kept me nice and cool.
There was excellent wifi (slight digression this week I have been in the USA on some AA domestic, cost of wifi was usd20 for 3 hours and quality was excellent - I listened to streaming TMS cricket live - come on BA get with the times !!). Interestingly the no smoking signs have gone, replaced by an electronic devices sign (when its lit up you cant use them). Again modern.
There were also large overhead tv screens with flight map and info (so you could watch tv and just glance up for your map fix)
The lighting was very funky a sort of red white and blue.
The food was ok, I had a pretty good chicken tikka massala, wines a bit lack lustre.
Ok so what are the negatives ?
The drink and meal service took an age (limited lounge food so all ate that I could see) I was towards the back of J and they started at the front. We had the usual long taxi and only on takeoff did someone ask food choice, then eventually a cart with drinks, then later the cart with starter and salad. Then main course was hand served. Then drinks and then dessert cart. We took off at 1940, I didnt have a drink until 2015 and my tray was cleared at 2240. Luckily I am on hols so was ok but for work this would drive me nuts, interestingly very few were sleeping (not like BA where its lights out v quick)
Lighting, they never really went off.
Breakfast - only cereal and I said do not wake, but 2.5hrs before landing - I mean barely 2 hours after finished dinner they started the lights and carts so was disturbed and at 1hr 15 before landing was woken demanding headset back. i was a bit cross with this but was told people steal them. There was a booming PA too about headsets at 1hr before.
So basically whilst the seat is good for sleep - I found the padding far better than BA and not having the springboard effect was great too - AA basically dont really allow you to get much. I pointed this out to the Chief Steward or whatever they are called and he just shrugged and says AA travellers like service. He also said loads of these planes being delivered and all the LHR will go to 77W.
Sad to say but given a choice I would probably choose AA over BA now - but with good sleep mask and earplugs,and a vigilance on equipment changes old AA J not something to be recommended.

I think BA may well need to respond but perhaps the JSA with AA means they dont care so much ?