One great thing about android is the ability to make your phone into a completely new experience whenever you want.
Take this site for example... Beautiful Android Themes, Wallpapers, and Homescreens
I'll be honest and say it's a little harder to get bored on Android then it is on iOS when you look at all the things that can be done on it. Regardless of that though I always end up missing my iPhone lol.
The flip side, at least from *my* experience is that I was never satisfied. Don't misunderstand me. I thoroughly enjoyed my Android devices as smartphones, but I was never satisfied with the setup. I customized my devices every way imaginable, and I did it to the point where I spent more time customizing and flashing new roms than I did actually using the device and being productive with it. When I got the iPhone 4S, it allowed me to be productive and content, and I made the decision to enjoy it without ever jailbreaking it, and I've kept that decision even though I now have an iPhone 5. Endless customizations lead to endless tinkering which also leads to never being satisfied.