The TSA security line variance is much lower in T8 vs T7, and pre-check is consistent, so that is an improvement. Given that most AS flights will probably operate from the far gates of T8, that will add 5-10mins of walking, negating some time savings. The AC will be worse especially in in the early afternoon when it often gets crowded, but it has showers which is nice for the redeye passengers. So overall this is probably a neutral change for point-to-point AS flyers at worst, and good overall as it makes JFK as a more viable connection point and improves travel options. Much better for AS to be in the oneworld T8 vs isolated in T7. AS could maybe get a little feed from AA at JFK to fly passengers onward, especially if there's a pacific buildup in SEA.

Soho and Greenwich lounges are nicer but unless the rules change or AS pays AA/BA for access, they will not help most AS flyers (only non-AA/AS OWS/OWE have access on domestic & short-haul intl.) Someone could fly on AS/JL JFK-SFO/SEA/SAN-TYO (or in the near future, AS JFK-SEA-ICN/TYO) and use Greenwich/Soho though. Perhaps there' will be a carveout for J passengers on HA JFK-HNL to use Greenwich. Even without Greenwich I think this is a upgrade for HA flyer.

T7 is being demolished very soon so the only question was whether AS would end up at probably either T8 or the new T6. I suppose AS could still move to T6 when it opens, but it's probably more useful for AS to stay in T8.