The direction, the soundtrack, the voice acting, the animation are all top notch. Character development of the major characters is executed well, however, a lot of the of faces that we see on the show don't get enough screen time in my opinion.
With that said, I enjoyed all 3 season. I am a bit worried how the story is gonna wrap up now and how thrilling the last season will be now that the mystery is resolved. (which has been a big driving force behind the suspense and the thrill). LOST kept us hooked until we found out what was inside the hatch, I hope AoT doesn't share the same destiny.