Until January of this year, I had been using my original iPhone 3G. Last year after iOS 4, my phone started acting up horribly. It had constant lag, with me regularly finishing entire sentences before they would show up whenever I would type anywhere, my battery would last 3-4 hours max if I even checked my email or sent any texts, et al.
I expected to upgrade to the iPhone 4 until I learned that other phones even existed, due to co-workers having Android phones, so I decided to check them out.
What convinced me that Android was better for me that iPhone:
-Widgets, the ability to have all the information I need at the flick of a finger, without waiting for apps to load. Being able to see with a glance my calendar, weather, or local events happening through twitter feeds.
-Notifications, I despised the pop-up notifications in iOS, that would interrupt anything and force me to either stop anything I'm doing to respond or hunt down what had happened later. If I'm listening to Pandora and received a text I'd have to stop music and reload Pandora again.
-Access to my file system, I'm a bit of a nerd, so I love being able to transfer any file I want between my computer and my phone, whether to transfer to another computer or actually access on my phone. I constantly use this, to transfer music, pictures, and work documents. I cannot get iTunes on my work computer, so whenever I have to go away from the office, and get some light work done I can just put whatever I'm working on on my phone and access it via Quickoffice which came on my Atrix.
-Having multiple buttons, I love the hardwired buttons on Android. Whenever I use my iPhone now I'm always frustrated due to the lack of the back button. I love on my Android that my screen doesn't have the menus constantly cluttering everything, so I can actually see the whole webpage and only access the menu when I need it.
-Quick toggles for settings that I can have set on my homescreen, and within seconds toggle on/off wifi, bluetooth, gps, airplane mode, autosync, and brightness levels.
-Enhanced multi-tasking so I can actually get many things done at the same time, all without stopping my music (unless I have to make or answer a phone call).
-The ability to keep full tabs on my battery usage, as well as constant updates on any data that I've used, even though I have unlimited data I love knowing how much I've used.
-The ability to install alternate keyboards/browsers/launchers/dialers and actually have the phone set them as defaults, I currently use Swype, which I love.
-Console game emulators, I love the ability to play my old NES and GBA games on my phone wherever I go, and with root, I can pair my PS3 controller to my phone and use it to control the emulators.
Edit: I forgot to include another reason why I wanted to switch to Android.
-Tasker, allows me to automatically change settings based on real-world situations, for EX I can keep my phone ringer on all times but have it automatically set to vibrate when I am within gps range of work or during work hours, and silent when I am in a meeting. I can turn syncing off, and it will turn itself on only when I am plugged in to charge. I can automatically keep WiFi settings off unless I am in my house and/or in range of my WiFi network.
In all, the only things that iPhone is adding with iOS 5 are features which have long been implemented in Android, albeit with a little more cutesy bubbly aesthetics. iOS5 provides notifications, icloud interfacing (if you buy Apple's additional overpriced garbage), and wireless syncing/updating. With all of the other OS features they're tacking onto iOS, there still is no urge for me to go back, because I hate the navigation through iOS, being restricted to app icon grid homescreens, with a single button that does nothing but take you back to your homescreen from an app so all you can do is open another app.
Also, not one of my reasons requires root to work. These phones have much more capability straight from the box, and the only way the iPhone can come close is through jailbreaking, of course then you can root Androids and get even more functionality then.