Got mine about 45 minutes ago so very briefly so far:
The Touch ID to unlock is super fast, works while charging as well.
Display set to 50% brightness indoors and I don't see myself going past that.
Apps and Music downloaded very fast.
Touch and drag from left sde of screen to get to opened apps works great.
Music sounds very good, I have a pair of Sony XBA H1s and volume set to 50% is plenty. Tried some classical music, nice full sound from the orchestra.
Additional weight versus the iPhone 6 is noticeable going back and forth but negligble. I like the additional heft to tell the truth.
Subway Surfers and Temple Run opened in about 2 seconds (no lie), RR3 took about 5 seconds.
Hey Siri works great.
More later!
Have you found it possible to double tap the home button to bring up the Wallet app without waking the phone?