it's not completly meaningless. By converting to 16 bit as your first editing step, you can avoid "banding" when playing with certain functions repeatedly (levels, curves, hue adjustements, etc). I'm sorry i dont have an example at this moment, but i's been helpful for me in the past..
Typically your camera produces 10bit or 12bit images.
If you use JPEG mode, these are automatically compressed down to 8bit colour (losing some subtle tonal ranges)
If you then go on to manipulate things, doing levels or curves adjustments or similar, you are effectively stretching and compressing the colour information in the image. Working in 16 bit mode during this means there is a wider range that this information can be moved around in, until you finally compress it down to 8 bit mode.
So, if you don't do much in the way of changing colours, brightness, contrast or anything else that adjusts the image histogram, there isn't much point working in 16 bit mode. If you do tend to make changes, 16 bit mode means you will preserve more of the subtle tonal range within your image while working on it, so that you'll get the best possible result when you either print or save as an 8bit JPEG for the web.
Gordon, that's about as clear an concise an explanation of this as I've EVER seen. Glad I did not reapond first, since my response would not have been nearly as clear.
