You'd be amazed at how useful a nearly point-blank rock can be, when used sparingly as a surprise attack. If they're expecting a bair or something, they might spotdodge, but the rock is laggier, so they would get hit, or at least get their shield hit, which usually knocks them back far enough for you to have time to transform back.
I try to only use it about two times during a match, and occasionally more if it's an attempt at an offstage gimp. Nothing's more satisfying than koing a meta knight offstage with rock
Well, other than Koing him with Toon Link's down air.