Thank you very much, these nodes will be very helpful. I have always wanted to have inputs into the vector Mapping node, to allow more control, and this does exactly that. And thanks for explaining the difference between Point and Texture mode, had not seen that clearly anywhere else before.
One minor point on the first example in Using the Custom Transformation Nodes, in theory I thought you can achieve the same effect by turning off Auto Texture Space in the Texture Space panel in Object Data, and making sure Locations X Y and Z are set to 0 and Size X Y and Z are set to 1. This is a more flexible solution as the texture then follows the shape whichever way way it is distorted, although it doesn't always seem to work for me so I must be forgetting a setting somewhere.
The portal example is very cool. Will have to try something similar.
That looks like a good solution! Though it doesn't look like that method doesn't handle rotations. However, it's nice to be able to have that visual representation. So, I guess it depends on the project! As for it not always working, I think that's a bug and I've reported it to the devs.