Played with them in the store just now. 6 is the perfect size for sure. IPhone 4s and 5 size lovers be damned. It doesn't even feel big, the 5 and others just feel small.
But the plus... Haha damn. Right now it doesn't demo so well because there weren't any apps designed for the size. So everything including text just felt jumbo. Couldn't use safari much since the store was packed and their wifi wasn't working too well.
My thumb felt pretty good using the keyboard with one hand. But it definitely feels the most natural with two for sure. They did a great job with the thinness and weight. Felt good in the hand and mine are pretty average I think.
Tough decision. I'm on safari way more than using it as a phone, so that plus real estate seems awesome. But the 6 feels like the perfect phone overall, one that you can still carry anywhere, run with at the gym, etc