I have been using a $100 temporary Android phone while waiting for my fancy phone to get replaced under warranty and the experience with the stock OS is just so so bad. Like barely usable most of the time. Even the GPS and wifi don't work well.

Most people worldwide use cheap Android phones on old versions of the OS and this was a good reminder that just because my mobile app/site works well on my fancy phone, it might work hardly at all for most people.