I use this on Chrome to help curb my "tab junkie" tendencies, and was excited to hear that we finally had a FireFox version... It's a simple, elegant concept, which for some reason most other FF extensions had ignored. However, I currently use FireFox Tab Groups to organize my tabs, and when I clicked the OneTab button... it pulled EVERY tab out of the tab groups and into OneTab! All the organization of my tab groups was gone! Everything was just one big list of tabs! Long story short, I spent a not insignificant time trying to get my tab groups back, and finally ended up restoring a previous profile session. This worked fine, and I still would prefer to be using OneTab, but first I'm going to have to find out how to get all my Tab Groups pulled into OneTab without losing the entire structure.
I understand if one add-on doesn't always play nice with every other add-on out there, but Tab Groups is a native FireFox feature. In addition, it would seem likely that a OneTab user would already be included towards using Tab Groups to manage their overuse of tabs; it seems like a great oversight for OneTab to only pull tabs from the group currently open.