Libsass is night & day vs Ruby Sass. No problems using libsass with Bourbon, Bourbon thankfully stays away from the bleeding-edge features (many of which can be emulated with clever functions).

In a previous project, we saw Sass compiles go from ~15s to about 400ms by moving to libsass. Completely changes the development cycle (with HMR or livereload) as you see changes immediately.

I've been using node-sass (libsass wrapper) recently, which hasn't been too bad compared to less (which is native to node/js). Seems to be working fine with bootstrap-sass, and surprisingly fast, compared to less, so I imaging the ruby sass implementation would be similarly slow by comparison.