If you are going to be using it for running then I recommend getting an Nano and this:
http://store.apple.com/1-800-MY-APPL...re=MA365LL%2FB
The nike + system with the nano is awsome. It will tell you how fast you are running and keeps all you stats. Plus when you do a personal best you will get a message from Lance Armstrong telling you what a good job you are doing. Plus you can upload your stats and it will compare yours to others that have the system.