I tried this before and got overwhelmed by attempting to add permissions to all the sites I use. Of course, I read that initial setup could be an issue... I deleted it.
I have had this reinstalled for a month or two now and it is working fine. No slowdowns, only minor issues such as:
Finding that one site I need to give permission to so that videos play.
Not being able to block an entire domain (or not knowing how to yet at least)
Not being able wildcard whitelist things. If I go to a .edu site, I don't want to repeatedly find new scripts I need to add. I would rather whitelist all .edu sites while I'm doing what I'm doing so I can get to my required resources. (for the flamers, etc. This is my personal preference, it doesn't have to be yours. That is what flexibility in configuration is about).

Anyhow, it is still a good add-on... it just takes some adjusting to. I like the new UI and will be interested in seeing what new additions are made with it later!