I find this beautiful and pleasant to use, at least for a few nodes. At first it feels odd not to be in control of the exact location of some nodes, very much like when using Graphviz, but once you let go it becomes quite comfortable.

I wonder how well it scales for large numbers of nodes, for example when they need to be grouped, or hiding certain types of connections in order to simplify the graph in display. I am not familiar about d3.js, perhaps it already provides support for doing that?