I'm thinking about getting a smartphone (maybe an iPhone 4) and was looking at the plans at AT&T and Verizon. Both companies soak you but I guess you can afford it if you can afford the iPhone.
Do you reasonably need 2 GB, 4 GB, 5 GB? I don't see under 500 MB as being realistic but maybe it is.
I have wireless at home and at the office so I would only use the Wireless Data while not at home and while not at the office. I would like to use Google Voice for phone calls when on WiFi - does the iPhone let you do that? I believe that the Android phones allow you to do that.