I believe that it's more hype than concrete duplicatable muscle hypertrophy/regeneration/growth results.
IGF-1 is going to turn a dieting Bodybuilder from a fat oxidizer to a glucose oxidizer and promote cell storage and not influence lipolysis, but possibly be lipogenic.
So in the grand scheme of things -- could you use a few 100 mcg's as a "glucose disposal agent" to load some carbs in a depleted/lean body? Sure, and it should be much "safer" than insulin if that is a huge concern of not feeling confident with using insulin to carb load.
However - I think GH and simply using insulin is the magic, not any variant of IGFs
-FF