It´s true that the system isn´t as easy to understand as del.icio.us or other bookmarking tools. It takes a while until you get used to all those additional ways you can navigate through the system. Remember: “Twine looks at content and parses it automatically for the names of people, places, organizations and other subject tags. Users are then able to navigate between related content, view recommended content and connect with recommended people with related interests.” – But the “shortcoming” mentioned by Marshall Kirkpatrick that “… it’s hard to keep track of all the levels and types of information available” I can´t agree with: This has only to do with a general problem, which arises whenever semantic technologies should enhance the user experience. Either you stay with “simple” user-interfaces like Google or del.icio.us or you spend 5 minutes or so to learn a new piece of software which will help you to save time in the future and which helps you to find related information automatically.
On the other hand I was very surprised, that the automatic recommendations Twine makes on how to annotate or describe a new resource is really unsatisfying. Users will only spend time to tag their bookmarks if the machine comes up with some intelligent suggestions. And it´s true, as Marshall says, “most of the web is made up of ugly, non-standard pages.”
So hopefully Twine will add that feature before it will open up to the public (isn´t there a plan to integrate OpenCalais or something similar?), otherwise there will be no “first mainstream semantic web application” but only another prototype of a yet another semweb-app.