I'll second this. I switched from Jekyll to nanoc about a year and a half ago, and I'm very happy with it. I wrote a short piece about extending nanoc (to add categories) that people may find useful[1]. nanoc's own website has good introductory documentation[2], and the Github wiki also has good pages for examples[3] (sites that use nanoc) and samples4] (sites using nanoc with public source code).

[1]: http://ithaca.arpinum.org/2012/03/30/adding-categories.html

[2]: http://nanoc.stoneship.org/docs/

[3]: https://github.com/ddfreyne/nanoc/wiki/Showcase

[4]: https://github.com/ddfreyne/nanoc/wiki/Samples