I like Google products, and use them quite extensively. I use Firefox as my main browser, almost exclusively outside of work. It bothers the crap out me though that the functionality of Google Notebook is so bad in Firefox compared to IE.
I was really hoping that with the release of the Google Toolbar for Firefox 3 they would bring the Notebook functionality up to par with the IE functionality, but they didn’t. The main bit of functionality that is missing in Firefox is the highlighting that appears on the page when you note it in Google Notebook. This annotation is VERY nice in IE, but really non-existent in FF. If you look at the two screenshots below you will see what I mean.
Firefox 
Internet Explorer 