If I can have variables + nesting I'm basically good too. You can have both nesting and variables when using cssnext. See http://cssnext.io/features/#nesting and http://cssnext.io/features/#custom-properties-var. Variables in future CSS are called "custom properties".

I think cssnext is the way to go, just the same way Babel or Traceur is the way to go for JavaScript. Writing in the standard syntax makes your code portable and reusable.