As I discussed in my finance blog, I switched from cell phoneless to Republic Wireless in November 2014. I picked up a used Republic-compatible Motorola Moto X 2013 (1st generation) at a nice discount on Ebay, and it served me valiantly over the last sixteen months.
Now that I can buy cellular data by the megabyte, I'm using the phone quite a bit more and I decided to upgrade to the Motorola Moto X 2014 (2nd generation). It's an upgrade cascade: I passed my old phone to a family member to upgrade them from the Moto E, and their Moto E will go to grandpa so we can get him off of Consumer Wireless.