Rated 3 out of 5 stars

Unfortunately, it reduces the size of some windows, making some boxes/text go out of bound (check for example in "Tools"->"Options" -> "Composition"), even if all the options of the add-on have been disabled.

Thunderbird : version 3.0.1
OS : Windows XP SP3

This review is for a previous version of the add-on (0.1.9). 

could you try this and see if it makes any difference