I love my Iphone but I will tell you what can be improved on it.
1. The "edge" network is pretty slow. If you plan on using it for a lot of internet on the go, you may want to consider another option. It will pickup wi-fi if a router is around and the internet works blazing fast on that.
2. The touch screen interface takes a little while to get use to and is a little frustrating at first.
3. Any internet site that requires java, the application on the site can't be used. For example, I like to play games on yahoo but I can't on my phone. I also like to listen to my sirius over the internet but I can't on my phone because it requires a plug in.
All in all I'm happy with it and I will buy another one to replace it within the next 3 years when a better model comes out. I can even post on the RX from it! Every you tube video is now available and that is a great addition (only the top 10k videos were available at first). I think of the Iphone as a mini laptop. I don't know how tight your budget is, but you are looking at around 100 bucks a month for service.