Rated 3 out of 5 stars
Very nice for your most important bookmarks. There is however some place for improvement:
1. updating an existing thumbnail or folder with a customized images fails in many occasions with no clear pattern. Only work around is recreating the thumbnail or folder
2. Adding thumbnails to folders should be made much easier then it is now. All thumbnails inside a folder need to be created when you opened the folder. No moving around of thumbnails is possible. This really discourages the user to reorganize.