Personally, while I’ve always valued the site for its ability to store stuff, what’s always made Delicious most useful to me is its network pages in general, and mine in particular. It’s set up for one-key access in Safari, along with a very few other places. The lack of functional social features - it has a network, but you can only see your own, and friend finding is basically impossible - is why, despite the fact I signed up for Pinboard when it first hit beta, when it was still free, I never actually visited it. (Of course, that is to a large extent by design.)
I still find its pared-down interface slightly too minimal, and the ability to pull in feeds from Twitter and Instapaper has led to some people falling foul of link pollution. (If you could control whether links were marked as private per-service, that’d help, but for now that’s not an option.) (I should also admit that the prevalence of packratius links on Delicious proves that there’s at least some role for aggregation.)
Frankly, despite the burst of migrations, my delicious network is still more full of good links, although it’s been starved of some of the most interesting posters. I suppose I’ll either have to get used to hitting two pages, or relent on RSS reading and use Fever or some other aggregator. I’m annoyed that it’s come down to it, despite the fact I can see exactly why people have moved.
(As a side note, I think this also proves beyond all doubt how important the social aspect of any service is. For all that individuals can download their links, the value I get out of the site is not my 3,500 bookmarks, but the 345,681 in my network. The continued utility of that is what’s most at risk.)
Anyway, since Pinboard can mirror from Delicious but not vice versa, I’m going to keep using the latter as my primary service. Pinboard can carry on being what it’s been for the last eighteen months: a hot spare, but not the service I really want to be using.