I've often found that infinite planes behave like "finite" planes i.e. I can see the edges. e.g.

1. Load the "Dream Islands" from the "Landscapes 2" section of the Scene Wizard
2. Render - notice how the water plane (Infinite plane) renders as far as the eye can see

Now try this

1. In the "Displacement" section of the Infinite Plane's "tut1" shader, select anything from the drop down list - I selected "Natural Functions | Water Waves".
2. Notice how the "Preview" changes from an infinite plane to a normal plane with visible edges
3. Change the "Displacement" setting back to "None"
4. Render

The Infinite Plane has become a normal plane!

Any thoughts? Am I missing something or is this another bug?

Thanks
Richard