Works very good!

This add-on seems to rely on an internet service to function, meaning when the server goes down you lose access to your saved tabs. I'm not sure if it even stores a local copy of saved tabs, because when the server went down (the entire website was suspended by the server host), all my saved tabs vanished from the add-on. As soon as the service was restored, I moved all my saved tabs to Tab Stash, which is an add-on that does essentially everything this add-on does, but without trying to get you to pay for a subscription, and without relying on a sketchy internet service that could shut down at any time and without warning.

I tried it out and it did not preserve the history of the tab, just its current URL, so after restoring I could not go "back".
Also, I saved an entire window which had 3-4 tabs with paused YouTube clips; when I restored the window, they all started playing - Chaos!
The description uses the word "session" but this is misleading, as it is basically just a glorified bookmarking tool.

Disapointing.