My review after using the iPhone 6 since last Saturday, 20/9/2014.
1. Size wise, takes getting used to. I don't have large hands and feels odd when my thumb reaches for the nos for pincode. Now have resorted to fingerprint ID. For me, no more single handed use. Again, will take getting used to.
2. Battery - I would say it lasted me significantly longer compared to my iP5, despite meddling with it continuously.Thumbs up for me. Hate phones that won't last me the day.
3. Camera - focuses faster and quality is better than my iP5. Can't believe it took Apple till iOS8 before implementing timer. Front camera definitely would be attractive to those loving selfies, but personally, not wide angled enough for groupies/groufies .. whatever you call it

Thumbs down for the front camera.
All in all, the hardware isn't much to shout about. The bigger screen does help a little bit with viewing. But iOS partially resolved that when I was using iP5 by allowing bolded text. That helps especially those who struggles with small words. Being thinner, I am now starting to wonder how much thinner it will get before it gets too flimsy to hold, especially when taking selfies.
But thumbs up for its build quality. Direct competition for latest HTC One. Samsung? Not there yet when it comes to craftmanship.
At the end of it, it boils down to package. iOS works well with the hardware, right from the very beginning of iPhone to current version. Can't say the same for other phone makers, which I have tried (HTC/Lumia/Sony). Sammy? No good reviews coming from my colleagues who uses mostly S3/S4.