That said, it is mostly good enough. I've used it for a few SASS projects in combination with Bourbon and it works great. IMO the huge compilation speedup (I saw reductions from 5-6s to about 200ms) was worth the slight move backwards in features. I became much more productive with a more responsive livereload.

Libsass is missing some hugely important features, but it (appears to be) in very active development and the disparity list is shrinking.

Even lacking missing those features, the 12x compilation speed improvement in libsass is pretty compelling.

The note is slightly outdated - the recently released libsass V3[1] is targeting SASS 3.4, and they expect to fully pass the spec by V3.1