I have had an iPhone since they first came out, so close to 7 years now. Always updated with the newest model, not because of the "cool factor" but because it didn't cost me anything. I would pay the $199, extend my contract, and sell my old phone for $200+ on eBay.
After using the same phone for so long the familiarity kept me tied to the brand. I can navigate through the phone without paying much attention because I know it so well.
That being said, I think I am jumping ship. The last couple iPhones I have got have been plagued with problems. From screens going out, to poor reception, to this most recent one that can not be off of a charger for more than a few hours. I know the phones well enough, that I can do my own repairs, I am just sick of having to do that.
So I think when the S5 comes out I will bid farewell to my old friend the iPhone.
**OT: When a loyal user like me is willing to jump ship... it's probably time to dump your Apple stock **