There are a lot of things to like about this script. There two things that I have found to be somewhat annoying.
First, it is not extremely obvious how to access the script configuration menu on my browser (Firefox 7.0.1). I eventually stumbled upon one method, finding a link in my public profile section on my 'Quick View' profile page. The About page makes no mention of this link. The author, Torsten Amshove, responded to my earlier version of the review and I was able to then find the other way to access the menu from any page where the script is active. In Firefox 7 the Greasemonkey appears in the toolbar and has a drop down list associated with it. Clicking the drop down mark displays a list one entry is 'User Script Commands...', clicking that will display the 'little helper config' button which brings up the config menu.
Second, the hide avatars functionality is redundant now that groundspeak has implemented this capability via a setting in the user profile. In fact this script overrides the setting in the profile with the settings in its configuration. This feature is redundant and should either be removed or should be reprogrammed to recognize that the option is set in the profile and give deference to it when set.
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