When we first came up with this idea, we really needed a good way to comment & annotate and keep all that feedback inline instead of it spilling over into email. The second is that we provide an easy way to diff revisions side by side or overlay them to see what has actually changed. Behind the scenes, we actually work quite differently from LayerVault, particularly on large files. I'd love to talk to you more to see how we can help you. Please email me email@example.com.