Apple iPhone 4 (GSM)

I am a long time iPhone user and I do love it. I also do not seem to have any problems with AT&T service where I live. I have also found that AT&T works better in the places I tend to travel to when I am not at home. When I had Verizon our phones would not work in Iuka, MS or in Alaska. Our iPhones work in both places.

Still, I am so tempted to switch to Spring and get the HTC EVO 4G. I am mainly interested in it for two reasons...the large screen and the WiMax service (I am in Portland, OR).

I need to make up my mind because my AT&T contract is up for renewal this month and I need to decided whether to stay with AT&T and get the iPhone 4 or switch. Since I am grandfathered in I would be keeping my unlimited data plan with AT&T so that is not an issue.

I mostly use my phone as a web browser and a phone. I do not play video games so alot of things the phones can do make little difference to me. I just basically want a good phone that is also a good internet device.

Advice?