I absolutely HATE the power button on the side. Half the time when I push it, the other end of my hand ends up pushing one of the volume buttons.
Also, when I use the volume up button to snap a picture, sometimes the other end of my hand pushes the power button.
Landscape mode on the home screen is driving me crazy. I thought I would like it, but I don't constantly moving back and forth to portrait. If I am in an app using landscape and I push the home button, I am used to seeing it automatically go back to portrait. But instead it is in landscape. It would be nice if there was a way to lock just the home screen orientation and not the rest, to make it work like all other iphone models.
Changing orientation while watching some videos (I think it was in facebook), pauses the video and/or restarts it.
Email app doesn't show the status bar on the top in landscape. Not sure if this is an ios8 thing or what, but it is annoying.
Personally, I think the phone is too big. I have big hands, but I cannot use it safely in one hand. I can't simultaneously maintain a good grip while using my thumb on the screen.
Battery life seems like all other iphones that I have had when they were brand new. We will see in a few months from now after several charges where it stands. Although, I am already thinking of getting the 6 and selling the 6+ because of mainly the size. It just doesn't have that "convenient" feel to it anymore like my 5S did.
Now for the positive. Screen is great. Nice for viewing videos, pictures, and reading larger text.
I would like to see some sort of a slim case that has something like a handle on the back, or a little tab that snaps open and closed. This would allow for one-handed use while maintaining a safe grip. Meaning, right now, I can wrap my hand around the back and have a good grip, but then I cant use my thumb on the screen. If I could grip a handle on the back that would not require me to wrap my fingers all the way around, that might make me stay with the 6+ instead of the 6.
For example, imagine a case with a belt clip on the back. You could use the belt clip to help grip the phone. But something with a lower profile would be good.