I have two views on this:
1) It does work well for keeping you from wasting a lot of time on shopping or social media sites.
2) As someone who suffers with anxiety, I nearly always run out of time on social media sites (I usually give myself 15-20 mins a couple of times a day) because I am second guessing or rewriting a post. This isn't anything wrong with the plug-in itself, it's just that someone else with anxiety might run into the same sort of thing.