I’ve been using LessC for a while now, and the nesting expressiveness has made a frackload of difference.
That said, when I’m working with the transition to a mobile space, the scary part is the way one must master the cascade and know the specificity rules. “@mobile #some-item” and “@landscape #some-item” will have different specificities that can be exploited by the appserver developer, but learning those rules is daunting… and now necessary.