We run a wide range of Echo devices and actually prefer these 3rd gen Dots to the latest 4th Gen Dots.
Other than moving to a proprietary wall wart (from standard micro USB power), the 3rd gen addressed every shortcoming of the prior 2nd gen Dot. Then the 4th gen Dot moved to the truly oddball globular form factor, similar to Apple. And since the entire surface is covered in fabric it is a dust-collector with minimally improved sound quality.
If we needed more Dots, the key question is would we pay $20 for a used 3rd gen vs. $25 for a new 3rd gen that seems to be available everywhere?