I would... if I didn't live in a third world country (Canada). We're not getting it until the second round... :(

The iPhone 4 is a superb. Wonderful because visually beautiful and technically efficient.

The iPhone 4 is thinner than the iPhone 3G. The screen offers high resolution Retina exceptional (960x640 pixels, higher than its competitors who are 800x480).
I noticed some problems with the proximity sensor. During certain phone calls, you can press randomly and inadvertently buttons that lead to undesirable actions (such as the hookup or the speaker).
I also regret that the speaker should not be more stronger (although good quality).

I was rather BlackBerry, I see a great advantage to the iPhone. For techies, it's a phone sexy and powerful. And for beginners, once the initial settings made (possibly by being helped), the device is very simple and intuitive to use. The iPhone can receive broad categories of customers. This is what makes his success.
A word about the problem of antenna that has a lot of noise at launch. I do not think the iPhone has more than four more problems than the iPhone 3, quite the contrary.

I type slower than a real keyboard, the BlackBerry (it's a bit frustrating) and records management messages is not as good, but for everything else (browser, applications, photos, videos, etc. ...) iPhone 4 is much better.