I am a recent android convert. The reason is very simple - for me what I use is defined by what I can have and not what I want.
I will argue that iOS has been a really awesome companion for last four years but there were occasions where I struggled with the lack of free apps, On the other hand I found that there is no dearth of free apps on android. So my latest Samsung Galaxy might not be as easy to use as my iPhone but I have a much larger variety of apps to select from.
Once you get used with android you'll see how much of a difference it makes in customization.
Yeah, you are right about that. This is my second month using android and I can already notice the great amount of adjustments I can make to my specifications. Quite great actually! I should have mentioned that in my answer as well :-)