I love Instapaper. But only for reading things later. It's not by any means a Delicious replacement.

I use Delicious as an extension of my memory. I tag articles, blog posts, documentation, news … according to their key content, or at least according to the key aspects that I think might ever come in handy. By looking up Delicious bookmarks through the combining ("AND-ing") of tags, I can find back anything.

It has saved me countless hours by now. I've accumulated about 6000 bookmarks over the last few years.

What is missing for people who use Delicious like this, is a way to send things you've read in Instapaper to Delicious. Because one often first has to read something, or at least skim it, to determine whether it might come in handy in the future. Hence: Instapaper first, Delicious second.

Currently that step is an extremely frustrating one. There is no elegant solution.