I just scored an Amazon Fire Phone when the cut the price for a brand new unlocked device (32 GB) to $189 from $450 for a day or two. It's to replace the HTC One (M7) that became unusably slow after an update to Android 4.4, and also a cheap $200 Samsung Core II DUOS that I got abroad as a travel phone (painfully slow and laggy).
The big deficiency is that it does not have the Google Play Store. Turns out, on Amazon Fire OS 3.6.8, no rooting is needed to "sideload" apps. You do have to download APKs from a non-authorized source, though. You can get Google Play Store by the method in the video below.
Once that is installed, you will need to generate an application-specific password to sign in to the Play Store.
UPDATE: Well, I've had this for a couple of hours and there are major caveats. Some of the Google apps will not work, as they require a newer version of Google Play Services, which crashes on this version of Fire OS. Apps which do not work: Gmail, Inbox. However Google Drive does work, which is awesome.
UPDATE 2: More stuff which works or doesn't work. Dropbox, and Ingress work. So do Swarm, and Instagram. Instagram does not do location, however. I was surprised by Ingress because Google Maps (and My Maps) does not work. There seems to be an issue with handling location. It seems to be arbitrary which apps will work, and which will not.