Phenomenal. And entirely created with Blender, an open source software.
Sintel is the third short movie (after Elephants Dream and Big Buck Bunny) created with support of the Blender Foundation. The movie is created with the open-source software Blender (and other open-source tools), as always, all parts of the movie will be released with a Creative Commons Attribution 3.0 license, this means you can freely reuse and distribute this content, also commercially, for as long you provide a proper attribution.
More info here: http://durian.blender.org/
The YouTube channel by the BlenderFoundation can be found here http://www.youtube.com/user/BlenderFoundation in addition to the movie, you will find a lot of cool “making of” clips there. Go check it out!