Princess Tutu has an effective original premise in the blending of ballet and the dark side of fairy tales. Focused around Ahiru's struggles to get back the heart of Mythos as Princess Tutu while unaware of Drosselmeyer's manipulations, the mahou shoujo approach of Princess Tutu is quite different from other titles of the genre I've seen. Rather than having Tutu battle enemies, this title has her dance with other characters to help them figure out the internal conflicts they are facing and to calm down the intensity of their feelings from whichever part of Mythos's heart is consuming them. This approach does make Tutu have a "monster of the day" approach throughout much of the show's first half. At the same time, Tutu's four central characters of Fakir, Mythos, Rue and Ahiru get a good amount of depth and development as I was given enough sense of what they thought of one another from Rue's obsessive love for Mythos to Fakir's obsessive need to protect Mythos from obtaining his heart. There is also enough plot twists in Princess Tutu that maintained my interest in the series which leads to the series becoming increasingly darker as things progress thanks to later developments in the plot that affect the thoughts of the characters and cause them to develop over time, getting out of the designated roles that Drosselmeyer manipulated for them.
In terms of elements, Princess Tutu does well at sticking with its ballet and fairy tale approach. Elements of the fairy tale Drosselmeyer created for the town are present throughout this series where anthropomorphic animal characters and talking puppets blend in with human ones without anyone thinking how strange it is. There's also a brief dark fairy tale story told by a narrator at the start of each episode which provides some foreshadowing into the events that you can expect in each episode. Later facts that Fakir learns of his heritage also contribute to the fairy tale approach. The ballet approach is clearly shown through the ballet school that Ahiru and the other characters take part in as the series shows the rigorous routines and expectations of the profession. It blends with the fairy tale approach to look into themes of love and the overcoming of destiny that are commonplace with the romance genre. Blending with the ballet approach are classical music renditions that do well to flow with the mood of specific scenes seen throughout this series. I went especially giddy when I heard "Night on Bald Mountain" during a scene where Mythos was practicing his dancing during an episode in the second half of the series which shows the conflicts facing his character at that particular point in the story.
I can't say though that the show is a perfect masterpiece. While scenery was decent created with enough color and a good amount of detail, character designs were a bit on the simplistic side and for a title that focuses much on ballet, it makes use of enough still shots during the dance routines of a number of characters. In addition, the show's second half felt quite dragged out with the later developments coming from one of the characters as a number of episodes follow the same repetitious plot developments much like the retrieval of Mythos's pieces of heart by Tutu in the show's first half.
Still, these flaws shouldn't deter you from watching Princess Tutu. The blending of ballet and fairy tales is a fresh concept rendered quite well with fleshed-out central characters and enough developments in plot to keep you hooked on the series.