I feel that the battery life is not as good as iOS 5 was after all the updates. Also, the data connections seems to be laggy as where iOS 5 was pretty stable. The apps, even though they have been updated for iOS 6 seem to be laggy and crash randomly. I didn't have any of these issues before upgrading to iOS 6. iOS 5 was so smooth in the couple of months before iOS 6 was released.
I can't really put my finger on any one thing but this OS just feels like like it isn't at it's best yet or at least even close to it. iOS 5 felt the same way, and after updates, it got better and better.