Honestly if you had an iPhone 6 why would you upgrade? Better battery life is cool, and it being waterproof is novel. However, its basically the same phone for the end consumer.
That said, the new home button sounds very interesting (I say that both as a developer and end-user), and the new camera will be a very welcome addition. And battery life improvement on top that? Perfect.
It is an iterative improvement for sure, but I don't see why that's a bad thing.