Dark is one of the best show in Netflix that I have seen. The only negative I can think of is how hard it can be to keep track of all the characters across so many time periods. In season 3, at one point, I thought it was starting to become unravelled in its story telling, but it saved itself just in time.
The music is dark, the cinematography is dark and gritty. The characters range from odd, creepy, villainous to warm, lovable and interesting. The settings are a bit bleak at times and likely it's poorest point, but they did what they had to do and this was intentional.
I will miss this show, and at the end I both wanted and did not want (sound familiar?) a twist that might hint at a fourth season.