I had 500+ tabs and did the mistake of clicking this extension. I have another extension (Panorama View) which grouped them, but OneTab discarded all of that. I tried reopening them all, but Firefox crashed, and after restarting it, all of my tabs were gone. Oh well.
TL;DR: I lost every tab I had.

I am giving a 3 out of 5 (Down the Middle) The extension is amazingly fast to compile all the tabs into one tab but is excruciatingly painfully slow to restore tabs. Can this be fixed. Other extensions such as Tab Stash makes One Tab restore speed look like molasses in deep space. Hopefully there is a fix for this as I like the bigger layout in the OneTab screen. Thanks for your efforts though.

stopped working after the last firefox update. The support team does not want to help much. Very upset

This app is totally useless and a waste of space. When you go to look for your tabs, half of the time they're missing anyway. Why doesn't Firefox change the settings instead and not allow sites like Ebay to open 50 million windows every time you look at a listing. The multiple windows never use to be a problem, so maybe Firefox needs to address this issue so we don't have to have useless apps like 'One Tab' taking up space on our computers just so Ebay can open another, and another, and another window that will be wasting up space in the 'One Tab' app.

Tabs in a private window are restored in a regular (non-private) window. This is extremely unwanted, violates privacy expectations, and is non-intuititve, Fetching site information (favicon) from Google without explicit user approval is clearly anti-privacy. Frankly, I am shocked and very disappointed that Mozilla awarded this extension a "Recommended" badge.

Sketchy privacy policy. Use Tab Stash instead.

Simple and great