I previously had a 6+, and now have 6S+
Thoughts:
Touch ID is insanely fast, I've got my own little mini-game going to press so fast it doesn't unlock - unfortunately it's 1000-0 to Touch ID.
Camera seems no different at all, which is a disappointment.
I can definitely notice a slight weight difference, but I like it. It feels more rooted to my hand now.
The best thing about Live Photos is the wallpapers, but unfortunately I was under the impression when your phone wakes to display a notification, or if you wake it, the live background would move. It doesn't, which essentially means you have a standard static background, unless your 3D Touch. What's the point?
Lastly, 3D Touch seems like it has excellent potential, but just from a couple of hours of using it, I wish I could customise which options it displays, for example with the music app, being able to have my last playlist as an option, instead of Beats1. On a side note, I find 3D Touch whilst swiping a weird action to master. It doesn't feel fluid or intuitive. But it's early days.
The phone is blazing fast, super stable and as excellently crafted as ever though.