Feels good: The body of the iPhone 4 is very thin, much thinner than the iPhone 3GS, which was already considered to be very slim. At first, it’s a little weird because despite the smaller volume, the weight stays the same. The iPhone 4 feels incredibly dense and solid. I got used to it after a few hours. The good news is that even with a case on, it should stay very compact.

New hardware platform: The iPhone 4 comes with Apple’s A4 processor, as found on the iPad and it also packs 512MB of memory, which is twice as much as the iPhone 3GS. The additional memory is probably most useful to accommodate the new multi-task capabilities of the iPhone 4, but it might also bring some added performance to the system. The A4 processor should also be faster than its predecessor (the phone does feel faster) but speed was usually not a real issue on the 3GS, so the difference is not eye-popping.