works Rated 4 out of 5 stars

Does not always work, then shows only gravatars, but not the photos from address book.
Posted a list of my addons here
Any restrictions for picture format, size etc.?
[EDIT] Does not choose the right (main) address book, if same addresses are in more than one address book.

This review is for a previous version of the add-on (0.1.2). 

Re: works

Would you be able to send me an e-mail with more details on what isn't working correctly? My e-mail address is in the Support section of the add-on page.

I have no control over the order in which address books are searched. This add-on uses the first contact found with the sender's e-mail address which is the same contact listed under "from". Try the Duplicate Contact Manager add-on to remove duplicates.

There aren't really any restrictions on photos; as long as you can see the photo in the address book window it should work (assuming that is the only contact with that e-mail address). If you try to use a huge photo (several MBs) from the web then it isn't always saved correctly.