Remember all that in one of the first shippuuden manga chapters Jiraya told Naruto not to use "that jutsu"? Well, I think it has nothing to do with the kyuubi. It's just some powerful uber jutsu that requires REALLY big amount of chakra and it's dangerous for the user.
Now that Naruto gained full access to the sage chakra he has "unlimited chakra" so he can use that jutsu: Naruto realized that himself look:
So? whadd'ya guys think?