The main reason I used Firefox was the Delicious integration. I am tired of Firefox opting for Safari on the Mac and Chrome on Win 7. I like what diigo has to offer but I would like an integrated manner to access my bookmarks. Is Safari not extendable to provide a bookmark tool?
On the Dashboard, but more importantly, on the Bookmarks landing page you need to be able search for a text phrase not just a tag. I would prefer the same input box as the tag filter but at a minimum I want a search box just for my bookmarks. Having the small site oriented search in the top right corner makes me feel this is more for a site wide search.
Additionally, I would like an AJAX search/filter mechanic. Instead of the normal HTTP post search mechanic, implement a realtime filter that display matching results as I type. If you limit the search base to the user's own bookmarks you should not have too bad of an hit on the backend.