My iPhone does everything I want to do on a smartphone

It works seamlessly with my work email and calendar, I get emails on my phone faster than Outlook, it integrates well with my Macbook Air, iTunes and Apple TV, takes great pictures, it is fast and extremely smooth in whatever it does, has not frozen even once in the last one year, has every possible app I want and then some, most of my relatives and friends use iPhones which makes iMessage and FaceTime really handy, heck I don't mind the 4" size even.

But why do I feel like I am missing out on something and still crave for an Android device? The iPhone, starting from the 3G is the only smartphone I've ever used, and have been extremely happy with my iOS experience. But the longing toward an Android phone is like an itch that I am unable to scratch. The pull of the Nexus 5/Moto Nexus is too great and for the first time in my life I may switch to a smartphone that doesn't run iOS later this year.

Anybody else in the same boat (wanting to switch platforms for no particular reason)? Is it a case of the grass is greener on the other side? Will I regret switching? What would be the biggest thing I'd miss from the iOS world by switching to Android?