One of the best addons I have ever used--probably would miss this as much, if not more than an adblocker. It's very effective at blocking distracting sites and the impact on my daily life has been significant.

As far as impact on the browser, LeechBlock itself uses very little RAM and CPU as an addon and it works very quickly (no delay in intercepting) in blocking websites. I also like that it just sits there in its little corner in my browser--no random alerts asking you to download another addon/write a review, ads, etc. like some addons.

The choice of features are excellent--being able to use wildcards to block the distracting pages of a website and allowing the productive parts is genius. The override and delaying feature is pretty smart too. I've used a good mix of all these features in the last few months that I've been using the addon. My favorite one is probably the "immediately block when conditions are met" since it just forces me to get off of social media and other distracting websites unlike other blockers that only block new instances of a website.

Overall, this is a very useful and very interesting productivity tool. It's unreal to see an addon of this quality being produced for free and I'm glad that it has all the features and customization that it has. It's definitely achieved its goal as a productivity tool and has easily cut my time on distracting sites.