GMarks can display the bookmarks almost the same as Firefox's native bookmarks: in a separate menu and in the sidebar. There's also a dropdown that can be added to Firefox's toolbars. The sidebar is useful when you want to perform full-text searches in your bookmarks without having to visit Google's site, while the GMark menu has an excellent option for managing bookmarks. If you click on "Organize bookmarks", you'll be able to import bookmarks, edit or delete bookmarks and create Gmail-like filters. For example, you can automatically add the label Google for any bookmark from this blog.
The extension can show the number of bookmarks for each label, a list of recent bookmarks and the most frequently visited bookmarks. To bookmark a page, use the familiar shortcut Ctrl+D or the GMarks menu.
One of the most frequent user requests for Google Bookmarks is nested labels and GMarks uses a little trick to simulate hierarchical labels: separate the labels with >. For example, if you want to label a bookmark as Shopping and Comparison, where Comparison is a sublabel of Shopping, just enter Shopping>Comparison when you create the bookmark. Since Google Bookmarks doesn't support this feature, the labels will appear to be nested only in GMarks.
And the cool features don't stop here: the extension suggests labels based on the web page's title, you can hide the bookmarks that have certain labels and there's an option for integrating the starred items from Google Reader.
Since the last time when I wrote about GMarks, the extension added the most interesting ideas implemented by the "competition" and managed to become THE Google Bookmarks extension. If there's anything that could be added, maybe it would be useful to completely replace Firefox's bookmarking system by hiding all the interface elements related to the native bookmarks and replicating all the changes to Google Bookmarks locally.
{ Thanks, Dr. Azrael Tod. }