Headroom is a very real advantage of recording in 24/96, but I think a bigger advantage is in post processing. Straight volume adjustments may be ok, but anything more sophisticated than that (EQ, compression, etc) will start to show the advantages of 24/96 over 16/44.1 in a hurry.
Regarding playback, a good DAC and well executed hardware design can make 16/44.1 playback sound absolutely fantastic, no doubt (provided the source is good). But the difference between good and poor DAC designs for 16/44.1 can be heard for sure. I suspect that the improved resolution of 24/96 should make it easier for the hardware designers to achieve higher quality playback, so I think that 24/96 will indeed make a difference in the average performance of mid- and low-priced playback systems.
I also suspect the very high-end audio guys may be able to hear the difference between 16/44.1 and 24/96 sources on their systems, but that's way out of my league.
- Dave