Here's a quick comparison between the redbook and HDTracks (24/96) version (originally released on a DVD video with "Advanced Resolution" logo?) of Buena Vista Social Club.
Associated equipment is in my sig. Only thing additional to mention: I was using the upsampler in PureMusic software such that the Audio GD interface is systematically fed 96kHz signals. Note however that the HD Tracks version is sent at native rate, not resampled in any way.
First off, it's a bit difficult to compare the two versions because the HD version is mixed with the majority of signal in the -15dB to -5dB region while the CD version is in the -12 to -2dB range. I tried to adjust the loudness as I could but this may not be perfect and play a role.
The very first thing I noticed is the same as usual: the instrument placement is much improved in the HD version with the instruments / singer moving a few feet back and playing in a well defined room while it does feel like you have your head right next to the instruments in CD version (while at the same time hearing a lot of the room acoustics though, so a bit weird feeling). In summary, depth, instrument placement and separation are improved in the HD version.
Another striking difference between the 2 mixes is that the 96kHz sounds warmer with the bass more prominent relative to the highs. What it feels like is that "nearfield" microphones are much more prominent in the mix of the CD version while the HD version relies more on "field" microphones placed more toward the auditor. These nearfield microphones give the CD version more sparkle and apparent impression of detail relative to the HD version. You read this right: relatively speaking, it first feels like the CD version is more detailed. But actually, it is not "real" detail, it's just that you hear more of the stuff picked up my microphones right next to the various instruments. Once you listen more closely to the HD version, you realize there is just the same amount of information, but it comes in more naturally as you always feel the instruments are solidly placed a few feet in front of you and a significant part of the sound is from reflections rather than direct field (including the transients). In summary, the presentation of detail is more natural in the HD version.
The last thing most noticeable during this short comparison was just how much more clearly I would hear the percussions (congo drums?) with HD version with individual hit of the drum clearly separated from the others. Also, the instrument has much more weight in the HD version while the CD is almost like cutting off the low frequencies in comparisons. I think this is again an artifact of using more the nearfield mics for the CD mix. In summary, well the HD rendering is simply more natural again.
I will conclude by saying that, if you don't have the redbook version, by all means get the HD tracks version as this is a must-have record and it sounds even better on the 24/96 format. But for those who have the redbook version and tight on budget, I'd say forget about the HD version as the CD is very well mixed and plenty good on its own.