I came from an iPhone 3GS (previously iPhone 3G) on AT&T. I was one of the people who thought I had the most modern, amazing phone and wouldn't dream of getting rid of it. iPhone 4 was the only thing on my mind on the horizon, and the only thing I thought existed that would satisfy my needs.
What actually originally spurred me to switch wasn't a phone, or features, but the plan cost. My wife recently finally got a job, which has saved us financially, but last month we were really biting our nails. On average we were spending $220 - $375 on our phone bill with AT&T, and it was the one glaring bill out of all of them (besides our mortgage) that I never wanted to come because it was so daunting.
But I just couldn't get rid of the iPhone, because as much as it was screwing us, how could I go back to a regular phone? I finally came to the point where I figured I'd be going to a basic phone out of necessity, but then I saw the EVO. I had never seen a phone with so many features before, and it was like a techie person, like me, made a dream phone with every feature people could have dreamed to have in a phone and presented it to me. Kickstand, HDMI out, huge 4.3" screen, HD camcorder, 8 mp camera, front facing camera, and an OS with running widgets and no restrictions.
I started researching the plan, and the good news was that it was cheaper. I was surprised to realize that not only did I have a 17% discount through my work, but the plan itself was quite nice. Unlimited talk to any mobile regardless of carrier, unlimited text without paying another fee for it