Naruto manga is about redemption and cooperation.
Kurama and Sasuke was the centerfold of that, Kurama was not a free (double edge gift, yes) powerup for the simple fact that Naruto could have lost control of him anytime, and it could have been Kyuubi attack on the leaf 2.0, so he kept Kurama and his malicious attempts at bay for the majority of the manga, and not to mention If Kurama would have been roaming free the Akatsuki would have captured him, and there would have been a one sided war, so someone had to carry him. Naruto did work for the power, him battling Kurama says that, and mastering the power to the point that no other jin did with their beast.
I don't get what the deal is, Naruto never used Kurama for his own twisted agendas (not that he had any), he only used Kurama for the most dire life or death situations, like protecting or rescuing his freinds, Naruto had power to cause havoc and choas, something most ninjas would have taken advantage of, but he did what is right, because it is right. He represents the ideal human, somebody whose ultimate goal is good.
Kishi could have written Naruto without Kurama, which would have come with its own set of powerups, but then again the theme of the manga is cooperation.
