" I can't think of any occasion where a real-time bump preview would be of any benefit"

I can.

There is a strategy for an animator whose look-and-feel is 'stylized realism." It consists of getting the software and video card to produce the best possible representation in the viewport at all times. Then........you render the viewport playback as animation.

Since "the system" has been optimized for fast response while engaged in posing, etc., you are talking about less than 2 seconds to "render" the viewport. Perhaps less! Add anti-alias and your frame render rate goes perhaps to 4-5 seconds.

Now....you can't go for photorealism. Shadows are a little bit of a problem. But.....if your ultimate "magic" is in postprocessing, guess what....you've got some pretty damn good raw footage at the cost of 4 seconds per frame. Open the sequence in AfterEffects and any 'issues' due to the fact that your raw was not actually "fully rendered" can be addressed in a stylized way.

Frankly, Poser is pretty cool for this technique. I've been using it. The new 2008 version of 3DSMax has advances in viewport realization which feed this paradigm.

This casts a whole new light on video card power, OpenGL implementation and feature power -- such as viewport bump/normal/displacement  in the viewport. Basically, it's hardware-assisted render of raw frames.

::::: Opera :::::