Damn. Rated 1 out of 5 stars

It ruined my settings in userChrome.css (Firefox 12)

.tabbrowser-tab:not([pinned]) {
max-width: 250px !important;
min-width: 1px !important;
}

Now the min. tab size is about 30 pixels and it can not be smaller, the stupid scrolling arrows on tab bar appeared again.

This review is for a previous version of the add-on (3.7.1).