Workaround for Firefox 4 Rated 4 out of 5 stars
I just edited the install.rdf file to make it work in Firefox 4. It works perfectly. Those who are interested can download this from → http://bit.ly/g7XRJP (after downloading the file just drag 'n drop it onto Firefox's add-on tab).
@Developer: The Unsorted Bookmarks folder is shown at the top of the bookmark menu. It'd be more preferable to have it at the bottom, to its default location.