There's some merit to higher sampling rates (contrary to Dan's contrarianism), but yeah, they lose me somewhere around 192 also. For playback, I don't see the point behind more than 96kHz, myself, but when mixing tracks, I understand the necessity of higher resolutions on the individual tracks as long as the mixdown software doesn't waste it -- you don't want to compound rounding errors. I'd have to do the math (which I have no interest in doing) to see what the necessary individual frequencies would need to be to get moar betr sound at the final mixdown.
I personally believe it reduces to phase accuracy, but that's just a SWAG.