I just realised that this project has been released under the mozilla github account — this (might) mean that it'll be actively maintained, and perhaps better documented than other libraries around.
Absolutely! The prefix is optional (but recommended). If you're comfortable with data attributes (or, they're required for some reason), thats cool too.
Performance of long CSS files isn't really the (major) concern —its how many _elements_ are being traversed (size of the dom) that really effects CSS-selector performance.
:thumbsup: Looks really great