It tried it right away and was wondering what this adds to my del.icio.us bookmarks. Not much, although I do find that Google Operating System missed an important feature. Because after you've shared a bookmark, you can also share that bookmark in del.icio.us, Facebook, etc. in a couple of extra clicks. Refer to the picture. This is my Google Shared Stuff.
UPDATE 9-21-07: Multiple social bookmarking can also be done in this way. And ReadWriteWeb has an interesting post on Google Shared Stuff.