In my opinion, the icon is too large at 24 x 24. Other Firefox toolbar icons are 16 x 16. I used the following CSS in my userChrome.css file to make it the correct size:
width: 24px !important;
height: 16px !important;
It would be really nice if somebody could rewrite this as a Greasemonkey script using Desktop Notifications, so that I could use this with Firefox.
In case that last part left you thinking that there's something wrong with me, take a look at this. :)