Blocks websites very effectively. I mainly use it to stop myself from binge watching YouTube videos. I have an endless supply of procrastination, and I'll usually find myself wandering into YouTube land if a web page has an embedded video. I have the app redirect me to a more helpful website, which happens to be Khan Academy right now. This little boost in focus has significantly reduced my wasted hours online. I use Chrome only to watch YouTube now, which works out well for me.

One note, you can't add blocked sites in the preferences of the app. You must right-click the page and select 'Block This Domain' in the drop down menu. Then you can go to preferences and redirect to another site instead of simply blocking the domain.