The folks at MacRumors have managed to get their hands on a physical mockup iPhone 6 based on leak drawings from Japanese website MacFan.
According to the report:
The larger iPhone definitely makes one-handed operation more difficult, even for relatively large hands, but many users are already accustomed to using two hands much of the time. With the larger body, Apple appears to be shifting the sleep/wake button from the top edge of the device to the right side, and this new location feels very natural in our hands, with the index finger sitting right on the button in a left-handed grip.
Our physical mockup includes our mocked up home screen showing that a 4.7-inch screen at the same 326 pixels per inch as the iPhone 5s would yield a 1334×750 display that could display an additional row of icons. While the mockup is based on the design drawings posted by MacFan, we did elect to slightly depress the surface of the device in order to help its physical features stand out more.