I got the iPhone cause I didn't like carrying an iPod and a phone about at once. I don't have alot of music so 16GB is enough for me, and the iPhone is just so easy and perfect for me. I can't stand using any other phone now.
I've bought every iPhone that's been out on Pay as you go here in the UK, So I didn't have the original iPhone, but I've bought the iPhone 3G/3GS/4 the week they came out, and gave my old iPhone to recycling companies and put the money they give me towards the new iPhone.
I love the iPhone 4. Have no proximity issues, camera issues, and the antenna issue doesn't really bother me, even though it is present in my iPhone.
I don't know what I'll be doing for the next iPhone. I'll wait till the keynote event and decide then. The iPhone 4 to iPhone 5 will probably be like the 3G to 3GS.