Compared to his Part 1 improvements in a massively short amount of time? His time-skip improvements are pathetic if you can even call them that.
I'm not very impressed.
I agree.I hadn't set high standards for Naruto's growth over those two and a half years so I was satisfied when he performed the Oodama Rasengan and showed other areas of improvement. Soon I became quizical about his growth because it lacked in comparison to Sasuke's. Sure Sasuke's growth was deemed irregular, but Naruto managed to keep up with him every since the manga began. I then realized two things:
a. Jiraiya's focus was more on training Naruto to master the Kyuubi's chakra. With the seal weakened, most of this training was null.
b. It wouldn't make sense to make Naruto the strongest when he plays the role of the underdog. Just watch, by the end of the series Naruto will be recognized as the absolute strongest.