To be honest I have an iPhone and it is AMAZING!!
It has all the capabilities of an iPod and more. With the iPod you can connect to the internet with wifi only. So if you are not in a wifi zone and need the internet you are SOL. With the iPhone plan that I have, I pay a flat rate bill per month. The contract includes unlimited calls to other t-mobile users, unlimited texting, and internet. Internet on the iPhone comes through the phone line and so as long as my phone has service I have internet access.
The other good thing is the applications. Some of the apps on the iPod need internet connection to work. Again if you are not in a Wifi area you may not be able to access them.
If you are going to pay that kind of money for an iPod you may as well get your moneys worth and go for the iPhone!!