Cons:
- Bad privacy, grabs website logos online from a server and allows that server to track your IP, one's fav sites and how often one accesses them. This is not compliant to GDPR's data minimisation and data transparency principle. Better would be to store and load website images locally and not establish an online connection by default.
- Loses settings when cookies are deleted for privacy reasons
- Tracks usage by unique(!) User ID in Local Storage, a no-go!

Pros:
+ clean and lean look and feel of that addon which is why I tried it.
+ not bloated with lots of useless features which is also a plus.
+ It does its job (and works in FF 71, too)