I like Cook's confidence, and I don't doubt he's correct, but this is the first time since iPhone 3G, and as a longtime Apple fan, that I'm considering an upgrade that is not an iPhone.
For me, it's too little, too late.
I'll come out and say it straight up, I think the design of the 6 is ugly - the plastic lines totally ruin it. I think their design started going downhill with the 5 and this cements their descent into Ugly Phone territory.
iOS is looking tired and outdated, despite the recent revamp. Pay piques my interest (coupled with Touch ID, which I haven't had the pleasure of using as an iPhone 5 user), but here in the UK, where we have contactless payment cards, I'm not sure it's such a big deal.
Everything else about the 6 seems to just be about playing catch up (and failing, in some respects). But due to Apple's incredible brand cachet, everybody's going wild and will treat it as the second coming.... (or 12th or whatever release it actually is).
I'm looking at the Xperia Z3. I know it's not out so I can't say with certainty, but all signs point to a better camera, better battery, better screen - the things I actually care about - and in my opinion at least, it looks miles better than the iPhone 6.