I had an iPhone 3G before the Fascinate. I loved the iPhone when I first got it 2 and a half years ago. Over those 2 years, though, there were some annoyances having to do with usability - no easy way to quickly turn WiFi or GPS on or off, or dim the screen, or lock the orientation sensor. Everything was burred deep in menus and Apple refuses to allow things like widgets that could address that.
Increasingly, it was becoming clear that it wasn't my phone, but essentially on loan from Apple, and they controlled what I could and couldn't do with it. Ended up jailbreaking it, but things still seemed like a workaround.
So when my contract was up, I thought I'd try an Android. Yea, it's not quite as slick as the iOS, and I still had to root it to get it to do everything I wanted (full file system access, install programs to access my home network, etc), but after doing this, the phone is far, FAR more capable than even my jailbroken iPhone.
I can upgrade or downgrade at will, install different systems. On the iPhone, you could upgrade, but downgrades were always a major hassle, if they were even possible at all.
Android isn't without it's faults, but I'd never leave it to go back to the iOS. It's my phone and I want to do with it as I please. I know I'm on my own and don't expect Verizon to support it when something gets screwed up. That's fine with me, but if I purchase what is essentially a small computer, I take issue with some corporate CEO dictating what I can and can't do with it - after the point of purchase and after the warranty runs out.