19.
When the iPhone first came out I actually had not planned to get it, I was waiting for the OpenMoko, but development just hasn't gone fast enough with it and who knows when the public will be enjoying that phone. I loved the idea of an Open Source phone, but I also knew the risks of investing in such. I wasn't interested in getting a phone that used Windows Mobile and the other smartphones (apart from the iPhone) that do not use Windows Mobile just weren't that impressive or out of my price range (for me, I was still in a contract, so I unless I paid full price for a phone I wasn't going to get a new phone... obviously with the iPhone that wouldn't make a difference, but look at the cost of some of the other smartphones out there and if you have to pay full price they can be VERY expensive).
So anyhow, that takes me to the point that I had done a lot of research before going in Monday to the AT&T store and I was in there for less than 10 minutes. But I will say to the OP that I don't think there is anything wrong with asking the salesperson if you should buy the phone. Perhaps I wouldn't use what they said to base my choice, but hearing their opinion could be worthwhile. The same is true when asking questions about the EDGE network and such, while we know their answers will be biased it might be worthwhile to hear what they say. As for Credit Check, I still have never understood the reason they do a credit check, if you sign up for a contract and have bad credit, you are still required to pay them monthly to get the service, if you stop paying you stop getting the service. If you break the contract they charge you $175. I understand the idea, if you have bad credit chances are you aren't going to pay that $175, if you have good credit you won't want to risk it by not paying that $175. However, it is worth wondering, there are a number of people denied a contract because they have had bad credit in the past, could AT&T (and other phone companies that require the credit check) actually make more money in the long run if they stopped requesting the check?
Oh well, I passed my credit check when I did it almost a year ago to get my Razr, and I am not leaving AT&T anytime soon (since I just signed a new two-year contract when I got my iPhone) so they will keep getting my money, will be several thousand worth when it is all said in done.
As for the age and how it centers around the iPhone, it is interesting that the demographic is so broad. How many 15 year olds did you see walking around the the BlackBerry or Treo or any of the Nokia smartphones? The iPhone is appealing to a number of demographics. Perhaps I am just another Apple fanboy, but I believe that like with anything else Apple is again making an impact on the way we view technology, this time with regards to smartphones. The OpenMoko was a cool platform that I would have loved to stand behind, but they haven't done what Apple has done and that is to make a finished product.