Now the manual has some info re. the projection node, I'd thought it was time to have another look.
The xyz - uvw option only maps along the Z axis. How would you project from the y or x as well? You have to use the UV translate/rotate/scale options in the texture image node, not the projection node, so units other than scale are not available. The manual does outline this, but this is a bit of a limitation (The projection will map image textures to the (-1, -1)–(1, 1) range.)
That brings me to the fact the UVMAP node is deprecated. As it stands the projection node does not offer the same level of functionality (or ease of use? unless I am missing something) as the UVMAP node, in particular being able to use the LW T data. I've been opening older scenes and updating assets for use in Octane. Several of these have a single projected or cube mapped texture, which means all I have to do is add the UVMAP node, set it to LWT, and I am done.
Hopefully the plan is to leave the UVMAP node in place for the time being?