Def. not a useless feature. Sitting with a client with a architectural project and deciding where the shadows should fall in the viewport is essential. Have been working on a scene where the time of day changed in the different cameras. So every time I switched the camera I had to change compass direction and time of day. (So I had to switch to realistic shading, change the sun to something other than corona and switch on exposure control. Then when rendering remembering to switch everything back.)
So a feature that is very welcome.
:)