So Ill start by saying theres nothing wrong with this app. It just feels like what Delicious would loved to have made in 2008 or so. Its 2013.
The Core Data database under the hood is certainly fast enough, and its portable enough that I bet we see this on iPad and iPhone in no time, with lighting controlled by gyroscope or something fancy like that.
But the UI is so "not flat" it almost hurts. You get the sense, clicking through the app, that this is one of the first databases designed to slow you down a bit to enjoy the view.
Bonus points, for all the properties available and the list view, which can be resized to smaller height rows (for my 13" monitor) and right-clicking the titlebar lets you see the items properties in a table and sort by them (e.g. location).
But it feels like a "v2" -- better, just not the best it could be. That bookshelf worked so well for the first version, they cant let it go, but Id love to see a v3 that feels much lighter-weight, is cross-platform, perhaps even web-based. Thought Id write it myself so I just checked the AppleScript dictionaries: Delicious isnt listed. So thats one feature from v2 you might miss in v3. But as a tradeoff, theres likely an SQLite database you can work with instead, for those geeky enough. :)