The main issue with it is how badly they mangled Takeshi's backstory. It really makes no sense for him to be a Quellist, and changing the entire backstory of the Envoys was a mistake as well. They seem so lame as a generic freedom fighter group training in the woods. I also hated that they made Kawahara his sister on the show, as it really doesn't make any sense given her role in the story. The only change from the book that works really well is changing the hotel from the Hendrix to the Raven.
Visually, the show is spectacular. Fight scenes are good too.