ETradeSupply has posted a detailed comparison of the purported front panel for the 'iPhone 5' and the front panel for the current generation iPhone.
Looking at the display area the iPhone 5 glass front is 90.25mm long, 51.60mm wide, while the iPhone 4S is 76.65mm and 51.60mm. This enlarges the display area from 3.61 inches to 4.065 inches.
The iPhone 5 glass front is 0.1mm thinner than the iPhone 4S and has a higher transmittance. The camera hole is slightly smaller and has moved to the top center above the earpiece. In addition, the light sensor has moved to the left of the earpiece and is much smaller.
Finally, the home button has a diameter that is 0.3mm less than that of the iPhone 4S and the area around the button has been narrowed.
Take a look at the full analysis in the video below...