Congrats, delicious needs more competition in this space.  I started working on something like this with a couple buddies of mine about two years ago with the read sites later stuff, syncing across browsers, etc.  Our project, favtopia.com, ended up getting put on a semi-permanent hold as we had other things we needed to work on.  I think you guys are on to something really useful, with a lot of great features other offerings lack.  Just keep refining your landing page (and the rest of your site), making what you do really clear to your visitors, and I think you guys will do well.