I just spent a week using del.icio.us and I have mixed reviews. Over a long period of time, it is much more useful than the "bookmarks" available in a browser. For the sake of making bookmarks of commonly visited websites, I prefer using the links toolbar and abbreviating them. It's more accessible having the links right there at the top. For the sake of being able to find popular sites the del.icio.us site is helpful in that it offers you the ability to search for other's bookmarks. It's also a nice way to log an important site when you are out of the office. I like the portability of the del.icio.us site. After a week of trying the bookmarking tool I think I will use both the links toolbar and the delicious site.
P.S. This was my favorite part of the superbowl.