[randy909]

I've heard that one of the problem areas is that you can't make a perfect, colorless filter - one where 20KHz is allowed through but 20.001 is not. A filter has to slope down at least somewhat gradually. The more steep you make the filter, the more it colors (distorts) the signal around the cutoff frequency. One of the purported benefits to a higher sampling rate is that you can make the high frequency filter with a more gradual slope which introduces less distortion.

I realize any differences in this area would be very slight if they exist at all. Anyone know more about that?

Edit: Apparently no one can dell a difference in listening tests with well made equipment. Theoretically if a device was built using an extremely cheap filter you'd be better off with the higher sampling rate, but I can't find any real examples.