Great idea, too buggy Rated 2 out of 5 stars
It's a good basic tool, but not well implemented. It can hang the browser if you add to its blocklist while other windows are open. The "BlockSite has blocked elements of this page" comes up on pages that don't have blocked elements, when some other open page gets the message.
For the people who complain that it doesn't block subdomains, note that it needs wildcards, like "*.example.com", in the blocklist, to do that.