I see many reviews complaining about the sound quality of the device and although I agree, sound quality is not great. Well, the flex is not really a music listening device. I believe the intended use is to fit small spaces and nooks where your main Echo devices cant hear you, I mean just look at the attachments...motion sensor and night light.
Personally this works great for me, I have a "L" shaped corridor as I enter my condo where I have installed the Echo Flex. Before, Alexa would not hear me from my entrance (my Echo is in my living room and far away from the entrance). Now all I do is walk in, the motion sensor automatically turns on my corridor lights and then I just have to say "Alexa, I'm home" right at the entrance and my light routine kicks in. No more shouting or having to walk to my living room before I can give a command.