I <3 del.icio.us and I <3 PDFs, so you’d think that Yummy would be a natural match for me. With the advent of del.icio.us filetype matching, I don’t see much advantage over del.icio.us’s implementation except that it’s got thumbnails and page counts. That’s not much and it’s especially not enough to artificially separate out my PDF bookmarks in some sort of virtual recycling waste of time.
The advantage of a social bookmarking service is that it’s social: there’s lots of people contributing lots of bookmarks and the scale is the value. All of the del.icio.us knockoffs try to add a feature here and a feature there, but they’re little more than window dressing if there’s not a huge user base behind them. And there likely won’t be a huge user base behind them ever because you only need one bookmarking service and del.icio.us is it for now (okay, there’s Furl too but I’ve never met anyone who’s used or even heard of it).
Here are my del.icio.us bookmarks, if you’re interested.