Incompatible in 4.0b6pre Rated 5 out of 5 stars
Nice extension. I'd like to point out the address bar issue I've seen in the latest b6pre (version: 2010.09.10)
As you can see in this image, the rich list item is missing the url (only page title is displayed). Disable Omnibar brings back the correct behavior.
Please take a look, thanks.
Looks like the rich list item changed in b6pre. It needs to be checked an updated. Thanks for letting me know.
Edit: It has been fixed in the latest release. It should be reviewed and made public very soon.