I have been using mental ray lens shaders in Maya quite heavily for the last few years and I've really noticed an obvious lack of information available to Maya artists about texture mapping with the humble mentalrayTexture node.
A mental ray texture node is used as an alternative to a standard Maya file texture node in situations where texture sampling artifacts become visible. For example if you spend any amount of time using a mental ray lens shaders in Maya you will quickly come across a rendering issue that looks like a blurry line that runs through your surface materials if you use a standard Maya file texture node. If you switch over to using a mental ray texture node the artifacts disappear.
Jason Fletcher of TheFulldomeBlog has documented this type of artifact in his blog post titled The Infamous Grey Blurry Line of Fisheye Lens Shaders.
To make it easier to use mentalrayTexture nodes in Maya you can download the Domemaster3D shader which includes 3 native mental ray material tools in the shelf: a color material, color + bump material, and a color image sequence material.