Keeps restoring "non-grouped" tabs each time I re-launch Firefox, which is just downright annoying. In my findings, it seems to consume more memory, makes Firefox a beat slower and seems to not be optimized all that well.
Having said all this, I think this is an AIO Productivity tool which is a must have and is most probably the best "Collections" alternative we have for FF at the moment.
Uninstalled it due to the persistent issues, hopefully the devs address them soon.