The concept is great, the design is beautiful and it looks like a lot of thought and work has gone in to. A couple of things that make me take a step back are, like crux mentioned, a lot of buttons. I feel overwhelmed at the get go. If I'm bookmarking, I want to do it clean and fast. The second thing is just the mass integration of tools, almost as if its not so much bookmarking but more project management. Otherwise its great and I'm sure many people will use it.