Me too. I hate cases, but my wife is right when she says that its size means I am going to drop it more. I like the thumbprint too. But, it's lame that it is so wide that I can't easily hold it in one hand and press the button with my thumb.I'm caseless right now which has me a little worried.
You may not be using the "pinky bridge" iphone holding technique. I recommend it; more stability, more horizontal reach. And you don't sacrifice as much vertically as you might think (top right corner window closing, for instance) because you can double tap the home button, just tap not press, and shrink the screen. A feature I'm still getting used to.
So after a few weeks, I have to say that it still feels too big. Maybe I wouldn't want to go back to the 5s size, but something in the middle. The battery life and thumbprint unlock are great. But the phone is poorly designed. It would be so much easier to hold if the sides were flat. Also the buttons and the vibrate toggle have slop in them. No iPhone I used before did. Not a Steve Jobs product.
I know a place that sells iphone cases, I'm not sure if they have them for the 6 yet?