So far 5 stars, but I haven't used it that long.

It allows me to create groups like in Chrome, but unlike Chrome, these simple tab groups replace the all the previous tabs you have open (when you switch to a different group).

Other extension open them in a new window and load them all, which I don't want, I mean I have groups with 1000+ tabs in them and loading so many can crash weaker computers or cause certain websites to block you.
Others like Chrome open the new tab group in the same window making it cluttered and unorganized.

Your ungrouped tabs are not lost when switching to a group, but I still recommend creating a group for them, just call it 'casual' or 'random'.

And unlike new windows or Chrome tab groups the 'vacation' or 'job hunting' group you weren't supposed to be looking at at work can be quickly switched to/from and perfectly hidden.

I was afraid it doesn't have backup options, but thankfully it does.

This plugin and Download Manager (S3) made it so I can pretty much switch over to using Firefox instead of Chrome, and that's pretty huge.