I've been using Delicious since March. It was, I suppose, a consequence of my Twitter enthusiasm -- I heard about so many new things worth reading, and needed to put them somewhere, and was not sure where I'd be when I got the opportunity to read them. Delicious was the obvious next step.
Why Delicious rather than Digg or reddit, I can't say. Perhaps Delicious was at the top of my mind for no better reason than its cupcake logo. I keep my consumption of those things under control by means of a diet and a chocolate protocol (details on request) but I can still think about them. And, icing or no icing, Delicious turned out to be fit for purpose.
The Delicious pages from libraries are daunting examples to follow. The Haddon has a page of links, with no Delicious involvement, in its existing web presence, and I sometimes promote new discoveries by email & Twitter. I will think about what a Haddon Delicious page would do in or to that scheme of things.