GPRS is a fall-back network that is used when no Edge/3g network is available. It's basically a slower 2g network. Here's an article that has some info on the different network connections on the iPhone(E/3g/O)????????
Yup! I wish I could get 3G whilst at work, would help the quiet moments pass a bit quicker & I could use tune in radio! Infact I'd be happy with an edge connection at work, anything is better than that little 'o'...If you lived anywhere in Britain apart from a major city youd see the o most of the time.