The biggest reason I will not be buying an Apple iPhone is they are not on sell yet, but that is not the only reason.
Now that I have left the Steve Jobs reality distortion field, there are a lot of features that I do like about the iPhone. I think the interface for the iPhone is truly revolutionary. From the demo I saw at the MacWorld keynote, the touch screen makes since for the best user input device for a smart phone. I had a Blackberry last year as my primary phone, but I was never really liked it that much.
The iPhone is also missing a number of things that I have in my current phone. My current phone is a Cingular 3G phone. The iPhone is only an EDGE phone. It looks like Apple is compensating for that with WiFi built into the phone.
It also looks like you will have to be a Cingular customer to get the phone. I hope that you will still be able to buy the phone unlocked. I think it is good that it is a GSM phone. In the US, there are only two GSM providers I know about, but this is the standard used outside the United States by most providers.
Right now my next Apple purchase will most likely be a Mac Book Pro.