Really great. I got comfortable with it and had hundreds of tabs saved in different groups (I like how when you open the browser it has the tabs saved but only loads the tabs you actually go to in that session to save CPU usage and memory, and you can close Firefox and reopen it if you have too many loaded in memory). When some error caused it to lose all the tabs, I simply restored the backup because of the extension's nifty automatic backup. The only problem is there is no way to allow it access to files on my device, so if I'm viewing pdfs in a different tab group, and then go to that group, I can't see the pdfs again unless I manually copy the file path into the address bar to load them again, which gets tedious if I'm viewing several pdfs in various tabs for school. They should add the ability to grant that permission so that it will smoothly reopen pdfs just like it smoothly reopens websites. Fix that and 5 stars!