Like for del.icio.us there is a bookmarklet to post a web page to Shared Stuff. You can tag that page and add a description. for some sites a thumbnail of the page is displayed. But for now that is nearly everything you can do. It is not possible to edit the entries on your personal Shared Stuff page. This is only possible by using the bookmarklet on that page again and change the tags or description.
One interesting thing is that if the page you want to add to Shared Stuff already is in your Google Bookmarks the tags you us in Google Bookmarks are automatically added. If you change tags in Google Bookmarks tags are automatically changed in Shared Stuff and vice versa.
But items on Shared Stuff are not automatically added to Google Bookmarks.
On time it is a bit complicated that you have two places to store your bookmarks, Shared Stuff for the ones you want to share and Google Bookmarks for the ones you want to keep private.