It's very much a meditation on the gravity of the events of the first game. As such, it will inevitably disappoint some of those who were expecting a new adventure with Joel and Ellie. However, as a story that asks "what if the consequences of Joel's actions were almost the gravest one can imagine" I think it was about as good as it could be.
I took Abby to be a lost soul who was on auto-pilot until she could get her revenge, and once she did, she found a purpose for her life in protecting Lev. A satisfying enough arc, and though I'm not in the Abby fan club, by the end I wanted her to live.
It's Ellie's fate that might truly upset fans. She doesn't deserve it, and it's truly heartbreaking. I hope we meet a calmer, wiser and luckier Ellie in the future, and not a lonely, broken woman.
An unforgettable experience, albeit a not very pleasant one.