So I had a quick look at iPhone 4 characteristics, besides the fact it has a flashlight and front-facing camera, what are its main advantages over the older iPhone models (I have iPhone 3G)? Is it actually a tiny bit smaller than the older models in terms of screen size?
The screen size is the same. Other advantages include the A4 chip, longer battery life, four times the pixels (a.k.a. "Retina Display" with 960x640 and 326ppi, which supposedly makes it so the human eye cannot see the actual pixel barriers from 12 inches away if you don't have perfect vision), 5MP camera that can shoot 720p video at 30 fps, 800:1 contrast ratio, three-axis gyroscope, and it's a lot thinner.
The camera module is also backside-illuminated, which helps it take better low-light pictures and videos. Also, it's just a sexy, sexy phone.
An A4 chip compared to the pos in the 3G is like a Corvette vs a Family wagon. Processess are much more snappier, responsive....way more ram for that 4.0 multitasking. I have a 3G (as well as every model iPhone) and I think the 3G was a waste of an upgrade. In terms of generation evolution, it was pointless. It slow as hell and constantly needs to free space for even the most native apps. Unless you like launch times that you can count outloud. I'd say the best upgrade plan would be 1st to 3G S or 3G to iPhone 4 but I fortunatly got one every year without have to pay extra, same for the new one when it's available
I've heard from some people that have used the iPhone 4 that the screen is much better than the previous iPhones and the difference is instantly visible once you try an iPhone 4. This photo just shows how much better it will look.