Kidding, right? Rated 1 out of 5 stars

Useless.

No email alerts ever arrived (during weeks of trial).

The little numbers "1:1" that got added to the toolbar indicated nothing as far as I could tell; no change in the web page in question caused any change in these numbers.

Worst: the clicked-open report window showed me items on pages I had never attached to AlertBox.

All I got was a system tray pop-up every few minutes (with accompanying sound) whether or not the indicated page really had changed.

The online 'support' is equally useless.

Sorry. No pass.

This review is for a previous version of the add-on (0.4.6.20111013.1-signed). 

AlertBox currently lacks a good documentation which should be taken care of near future. That should answer most of your queries. Specific answers to your comments:

> Useless

Far from it. At least for current set of users.

> No email alerts ever arrived (during weeks of trial).

See http://pulsvu.com/node/1287. It maybe due to missed settings.

> The little numbers "1:1" ...

They indicate alert counts like: NEW:ALL.

> Worst: the clicked-open report window showed me items on pages I had never attached to AlertBox.

Not possible. An alert cannot be added without user action.

> All I got was a system tray pop-up every few minutes

They are alerts for content changes. If the content changes a lot you can target specific content using visual content locators. They are very handy.

If you need help, you are welcome at the "support" forum or send me an email.