I upgraded to a paid Historious account a couple of days ago and I just imported all of my 4000+ bookmarks from Delicious. What drew me to historio.us was the caching: I love the fact that all my bookmarks are cached.(1) Lately I've been trying to cut down on the information I consume so the lack of 'social' features doesn't really bother me -- right now I'm more interested in retaining the stuff that I've already bookmarked than in finding new stuff to read.

(1) It looks like pinboard.in has the same function for about the same yearly price.