While I still use iOS, I switched to my phone to Android full-time since November and I have to say I enjoy it a lot. I use a Nexus 6 and for me to go back to iOS and the iPhone, it would take a lot of persuasion. That aside, what kept me using the iPhone for so long was a few things. Top notch build, amazing design, unparalleled reliability (compared to Android), software updates and support, device support (Apple Store and online support), speed and fluidity of iOS, killer integration between devices, and the overall ecosystem.
I wanted to try something else for awhile, but honestly the ecosystem lock-in was insanely hard to get out of, and is a huge reason why I stayed for so long. I'm not afraid to come back, but with the rumor of the headphone jack removal, I may not be buying another iPhone.