I have the original iPhone (8 GB), 3GS (32 GB) and am now using the iP4 (32 GB). I'm keeping one in every form factor and sell the others (between myself and my wife). If the iPhone 5 comes out next year in the same form factor (like 3G to 3GS), I'll sell our iP4s and so on. It's pretty cool to have one in each design version. My observations so far: Original iPhone: Superior build quality and the most substantial/durable iPhone, but slipperiest in the hand. iPhone 3GS (and 3G): Most comfortable in the hand but subpar build quality. Most uniform in terms of looks (and photographs the best). iPhone 4: Build quality as substantial as the original but apparently less sturdy. The best-wearing iPhone (no scratches on the Apple logo or stainless steel frame after a couple weeks unlike the previous versions' Apple logo and chrome bevel).