I changed for a variety of reasons. First, I was concerned about long-term support for the FFE from Ford. Second, the trade-in was so good. Third, my carpool lane sticker was going to expire. And fourth, I wanted a Tesla. When I bought my Tesla, the $7500 federal tax credit still applied, so that helped in the cost trades as well. Although that isn't true, purchase price of a Tesla has dropped since I bought mine (although, the configuration I bought, Long Range Rear Wheel Drive) isn't offered any more.
I love the Tesla. 20,000 miles so far, averaging 235 Wh/mi (a bit better than the FFE). Way more fun to drive, plus the Autopilot feature is awesome, particularly on my commute in LA traffic. I wouldn't hesitate to buy another one.