OneTab is an extension to avoid. When it works it works great. Then you trust it. Then it lets you down.

Specific failure that I have seen several times: Several Firefox windows open with multiple tabs, go to OneTab Icon, Right click, OneTab->Send all tabs from all windows to OneTab. All windows disappear except for the OneTab window. Close out of Firefox, reopen. OneTab doesn't have those tabs that you just saved in it, neither does Firefox, you lose.