I did it about 18 months ago, never looked back, glad I made the change TBH
I'd had 3 HTC Android phones a Desire, a Sensation and a Sensation XE, plus I also had a Motorola Xoom Android tablet, but I was having issues with bluetooth compatibility in my E46 330d, tried a friends iPhone 4S and it worked perfectly. So I bought a mint condition used iPhone 4S for myself, to see how I got on with it, before comitting to a new phone/contract, but I liked it and 6 months later I got a shiny new 5S when they were released, which I have currently and love. I then sold the Xoom tablet and got myself an iPad 3, which complements the iPhone well, with everything mirrored on both devices with iCloud, take a photo on the iPhone, seconds later it's there on my iPad, same for messages, websites, etc, very slick.
Really easy transition to make, all my contacts were synced to my Gmail account, so when I logged into Google on the iPhone it saw all my contacts, I'd envisiged having to manually re-enter all my contacts, so was pleasantly surprised. Does take a little getting used to the minor differences in the operating systems, menus, etc, but it doesn't take long to pick it up, when iOS7 came out last year it was a more Android-like experience compared to iOS6 & earlier, so for you now with iOS8 it will be easier to adopt than it was for me going onto iOS6.
I'd possibly go back to Android at some point, I'm not die-hard loyal to either system, but for now I can't see a reason to go back and I'm considering upgrading to a newer iPad, what with the newer models just being released.