Note: Informal review for manga readers. But I removed all spoilers regardless.
Amazing animation and editing from start to finish. Even the animation in the exhibition match at the beginning was crazy good.It is also very fast-paced despite the 90 min length. The entire match proceeded with very few interruptions. There were the usual few timeouts, a couple of flashbacks, and very occasionally the scene switched to the spectators but the pace of the movie really amazed me. There were a few times I wanted to take a drink but so much was happening on screen and so fast I couldn't peel my eyes away. A couple of times they intertwined 2 separate scenes from the manga and somehow made those work.
In short, the movie made everything from the manga better. The execution and timing of the jokes were excellent. I laughed with the audience even though I've read the manga probably 10 times. Some people in the audience laughed every single time Murasakibara spoke. His VA is so frigging good with the deadpan delivery.
Practically every dunk and every dribble was beautifully animated. You'll definitely see a lot more ball-handling and dribbling than what you are used to in the anime series.
The heroic moments of a couple of individuals (you'll know who if you've read the manga) before they exited the court were so bad-ass. Music played a huge part in those scenes of course.
The movie largely follows the story and dialogue from the original manga with a few inconsequential details left out and some additional scenes written specially for the movie by Fujimaki (the author of the original manga) himself.
Also, note that there's a post-credits scene.