I have an iPhone 4, but I occasionally use a sim adapter and go back to my 3Gs when I go certain places that may damage my phone. Let me just say that the iPhone 4 is light years ahead of the 3Gs. Every time I switch to the 3Gs I can't wait to switch back to the 4. For me the biggest differentiator is the screen... I didn't notice this until I got my iPhone 4, but my 3Gs gave me headaches due to the low resolution screen and constantly needing to squint. The camera is much better, and the flash is very useful. And overall the design is just superior. You will not regret getting it... It's only April, and if the iPhone 5 really does come out this summer, and you really want it you can just sell the 4 and get early upgrade pricing.