Rated 3 out of 5 stars

I like this extension.

But since TB 3.1 it can no longer be installed as global extension (see http://kb.mozillazine.org/Installing_extensions#Global_installation). TB reports it as 'incompatible' with this version (tried TB 5, 6 and 7).

Single-user Installation works!?

This review is for a previous version of the add-on (1.1.3). 

Support for global installation is something that was removed from Thunderbird, Firefox etc (i.e. gecko). It is not something that can be affected by this extension.