I've just my iphone 3gs on orange,and i think it's miles better then any other phone. The one main downside is the battery life is rubbish, if your browsing or doing anything other then using to call people then you'll be charging it constantly.
You'll be on it on for ages checking out all the different Apps from the app store. It also has a built in GPS which is handy if your driving, no need for a satnav!.