Rated 5 out of 5 stars
Fails miserably on 57 for obvious reasons. Had it running on an older machine and aesthetically speaking this is one of the best extensions on Firefox for an "out-of-the-box-awesomeness" experience.
Highly recommend it for pre-57 installations and I am sure it will be as good post 57.
Thanks for the review! The beta version is now a WebExtension: https://addons.mozilla.org/en-US/firefox/addon/vivaldifox/versions/beta