Works great Rated 5 out of 5 stars
Works very well! On my mac it does seem to make an error noise even though it is successful. I notice another reviewer had a problem with popups not appearing. I have the same problem! I'm not sure how the other person was able to fix it though but it would be good to find out somehow! -Edit-They have now suddenly started appearing! Though they seem to look like growl notifications? Either way it's great!
The last guy who had this problem informed me his issue was caused by another extension that was incompatible with firefox and preventing the popups appearing. After disabling that extension (Growl/GNTP 1.2.5 for him) the popup messages started working correctly.