In the pantheon of series endings from best (Bob Newhart waking up next to Emily at the end of Newhart and realizing it was all a dream), to Game of Thrones, Lost, Dexter, How I Met Your Mother, The Sopranos, Seinfeld, and Quantum Leap, it was somewhere in the middle.
It was satisfying overall, and actually gave the ending Wicked For Good should have with the possibility of a "happy" ending out there, but not specifically stated. For Good was saddled with the ending they chose for the stage show, so the Duffers had a lot more leeway.