Review for CardBook by Tim Grady
Rated 2 out of 5 stars
The add-on appears to be quite powerful, but I am unable to find any documentation for it at all. The User interface is not sufficiently facile that it's obvious how to perform certain functions, such as importing the Thunderbird address book, or syncing multiple instances of CardBook.
The greatest tool in the world is literally almost useless if users can't tell how to use it.
To create your own collections, you must have a Mozilla Add-ons account.