Satoshi sent in the following article: Ekakiya, one of the famous Blender gurus, shows us a nice demonstration of material nodes, composite nodes and tangent bump mappings at BlenderArtists. It's quite impressive: not only does he show rendered images but also snapshots of these nodes. The snapshots are totally complex, but have comments to describe how the part works.
He has experience of node systems in other 3D applications and has been worked at lots of commercial projects, so he can create this amazing work! Also, he has proposals about node system and other features of blender. He told me them last January, sorry if some of them have been implemented.
Blender node system doesn't have any link-controlling node, so nodes(noodles) are easy to complex. For example, when using the ramp node. (Does Script node will work for it?)
2. Post-process node for Material. For example blur, gamma correction and sharpness. It'll be useful for reflection map of some kind of metal materials.
3. Easy way to animate parameters.
4. Multi uvs for LOD.
Or access to uvs for material nodes to select them.(OK, I know multi uvs has been already planned for next release ;-))
5. Value accepts n<0.0 and n>1.0