Too complicated compared to competitors.

This is the exact opposite of simple. Check Sidebery for the simple (and also faster) one.

Works flawlessly! My only complaint would be that it's a little slow to startup on HDD-based systems, and prevents tabs from loading content until it's finished "warming up" (which can take up to 30 seconds)

Not simple. It's hard to understand what it's even doing, aside from _definitely_ not what I want or expect it to do. The worst extension I have _ever_ installed, and I've installed some pretty terrible extensions. It's less than worthless. At least if it were just worthless, it wouldn't be a big mess to clean up after I uninstall it.

Excellent! It's a must-have for daily usage!

very counter-intuitive to use : if i wanted to group my tabs i want them in the same browser not in a different browser window

The most important addon to keep me in Firefox!

Needed to hop onto Firefox while Chrome was being a bitch, and this add-on allowed me to replicate Chrome's groups... somewhat. How to switch between groups took a bit of getting used to, and it's more helpful in some areas (i.e. creating groups) and less in others (quickly switching between groups). That alone would be a 4-star rating, but what drops it down is the difficulty of organizing tab groups in the groups tab. I can only organize it alphabetically, so I have to go through some hoops if I want my groups in a particular order, which is fairly annoying. All in all, a helpful add-on, if not exactly what I was hoping for.

gd, used for years

Nice extensions, allows to manage tabs much more easily. What I'm missing is ability to group tab groups together too - folders and descriptions for tab groups.

overall good but some minor issues exist such as problems with FB groups not being saved properly. Also the backup feature is completely broken. it ignores \ entirely so it keeps making new folders on the desktop instead of bakcing up where I want it to. been doing this all year

It is extremely useful, stable, easy to use.
I have been using it for four years now without any problems.
It can also create backups, which take almost no storage space.
Also fully open source and recommended by Firefox :)