I have an Iphone and I think its great, applications are cheap and very easy to download, some are just amazing.
For internet navigation i have found it the easiest phone to use. The phone pretty much owns, kinda like Ipods in the MP3 world.
The only downpoints that I notice are the touch keypad (although you get used to it) and the glass screen (I have dropped mine face first on the cement and I have a mass crack in the top corner, its insured so all good)
If you get one, i recommend getting a silicone case. I have never met anyone who owns one that doesnt like it. You have to take note that its a mini computer so it can run slow at times and needs regular re booting.