I have an iTouch, which basically has the same interface, and I don't have a problem with it. I do, however, hate the fact that the iPhone is its exclusive contract with AT&T. I hate AT&T for its abysmal customer service, as does my entire family. They once continued to charge my mom even after she got off their plan, then tried to make it look like it was her fault. I've even met a former AT&T employee who resigned in protest of the way they treat the people on their phone plans. The fact that you can't get an iPhone on a Verizon plan is the primary reason my dad and I never got them, and opted instead for Droid Incredibles.
Also, the new "antenna" bug in the iPhone 4 is utterly ridiculous. I'm not going to 'hold it a different way', as Steve Jobs puts it. That is nothing more than a holier-than-thou attempt to double-talk the blame for Apple's glaring hardware flaws onto its customers.
In short, I'm not going to waste money on a defective device manufactured by a corporation that doesn't give two cents about its customers so that I can use a phone plan provided by a corporation that doesn't give two cents about its customers.
The iTouch solves a lot of that, though. It's not a phone, and it doesn't have the defects of the iPhone, so I like that.