My first month with the Nexus 5x and Project Fi, and after a few minor phone number porting issues, I’ve had very good service.  I’ve used the phone for two plus weeks in the Philippines, and call quality to/from US was excellent.  Data was 3G, but I was on WiFi most of the time.  Unlimited and free txt makes it easy keep in touch.  The 5x performs well for my needs and use.  When I travel, I use a second phone with local SIM, so the 5x was not in constant use, and the Doze feature on Marshmallow worked well; battery use is very low when the phone is not in use.   The finger print reader is amazing…fast and very accurate.  Highly recommend the 5x and Fi.