My main frustration (when I only had an iPod Touch) was that it's very difficult to get onto the internet when you want/need to - you're completely reliant on finding a wi-fi access point and most of those cost the earth. Although you have to pay at least £30 per month for the phone, you can do as much web browsing as you like and it's normally easy to find a signal, especially in a town or city where you probably need the information most.