It was great at first but then whatever trial period there was on the premium voices ran out and after spending way, way too long trying to figure out how to purchase access to those voices I gave up and used Zira. Then today after using it for a couple of weeks it went buggy. The stop button and the forward and back buttons stopped working and the reading speed seemed to be off. Even closing the tab wouldn't stop it from reading. Finally had to turn it off in Firefox settings and just went ahead and uninstalled it. While looking for a way to get the better voices I found out FF already has a built in TTS.