Rated 5 out of 5 stars

Update for my previous review:
You are right. It did not work on Firefox26. The last working FF version with the old google toolbar is FF 25.01.
Also with the tweak of Tab Mix Plus you will lose the ability to drag a tab to put it on another monitor. (Actually it can be done but it will leave an empty tab that you can't close unless you restart FF.)

This user has a previous review of this add-on.