EDIT: Correction: 3.6, not 3.7 http://apple.com/pr has high-res PR photos of iPhone (400 dpi true size) and 5G iPod (can be scaled maually to true size--it's 2.4" wide like the iPhone). Both images seem to show the TRUE usable size of the display: they have an unlit margin around the screen, inside the "hole," which is more realistic than filling the entire "hole" like some mockups do. So although the screen image is a mock-up, the SIZE seems to be very accurate in those PR photos, with almost no margin for error. (No pun intended.) Measuring those images in Photoshop, I cannot escape the following results: 1. iPhone screen is almost exactly 3.6" diagonal, bigger than the 3.5" advertised. iPod screen is about 2.44" diagonal, slightly smaller than the 2.5" advertised. 2. iPhone and iPod have almost exactly the same screen width and DPI--with the iPhone screen being twice as tall. 3. iPhone screen is almost exactly 2"x3" (320x480). iPod has almost exactly 2"x1.5" (320x240)--or just slightly smaller (meaning slightly smaller pixels than iPhone). 4. That does come out to exactly the 160 ppi Apple advertises for iPhone (160 does NOT work out with a 3.5" screen, but it does with 3.6"). It also works out with the iPod's advertised .156 mm dot pitch. The iPhone's dot pitch is .159 mm based on 160 ppi, which fits with the iPod screen being slightly narrower for the same 320 pixels. So all the math works out to the iPhone screen being bigger than advertised: 3.6". FUN with MATH P.S., 10 keys in 2 inches (QWERTYUIOP) gives each key on the iPhone .2 inches of space (seems like enough, since it's harmless to hit neighboring keys along with the one you want).