JuSumPilgrim makes a good point that a preamp comparison test can't tell you how a vocal track is going to sound in the final mix. Lynn Fuston is careful (on the first track of his discs) to remind listeners that they shouldn't draw any firm conclusions about the sound of any of the 33 preamps or 49 mics that were tested based solely on listening to these discs; rather, he hopes people will use the information to point them toward further first-hand listening tests on their own.
I think that's a fair and honest way to present the set. To my physically challenged but fairly well trained old ears, all of the tracks sound "recorded." That's not a good thing or a bad thing, but at no time if I closed my eyes was my brain tricked into thinking that a person was standing in front of me singing or playing an acoustic guitar. 
Only three of the preamps made me forget I was listening to a recording and drew me uncontrollably into the music. However subjective that experience is -- dependent not only on the circumstances surrounding the recording, but also my playback (equipment, room, ambient noise, where I'm sitting, etc.) -- it is still extremely useful information to me. 
On the mic disc, Mr. Fuston admits that the 12 engineers assembled for the blind listening tests were frequently surprised by their own ratings (they rated the mics for themselves before finding out which was which). He suggests each listener do the same, and he offers no suggestions as to which he found better or worse. In fact, he said that some mics he had shrugged off as not worth using sounded great to him on these voices on that day, while some of his favorite mics didn't fare as well as he expected. He also admitted that some mics he thought sounded great, other experienced engineers in the room didn't like at all, and vice versa. The real gift of this set is just that: it comes down to listening, and to hearing what you like and don't like. 
If you visit a chain stereo or department store, you'll see a lot of inexperienced shoppers expressing approval for big, bloated, boomy one-note bass and brassy treble. The sound is incredibly inaccurate, unmusical and wildly distorted, but if the best they've heard before was a portable stereo or the sound coming out of their TVs, it's completely understandable why they think it's good -- it has what their prior experience lacked. I'm not saying that's a bad thing; if it's what they like to listen to, then the market has met their needs successfully.
But if you're a musician who is recording, or if you are a listener who wants to hear something that resembles what a performer actually sounds like, accuracy becomes more important. For the musician, it's having some control over what your audience hears. For the listener, it's actually getting the musical message. If the message is funky, bassy, distorted and EQd into a happy face, then that's the way I want to hear it. If it's simple, acoustic and clean, then that's the way I want to hear it. Either way, I'd like to hear what the musician intended. 
Mics and preamps all have a different voice, whether we have good enough ears to hear the differences or not. There's nothing wrong with choosing a preamp that colors sound the way you want it to be heard. 
I guess that's why even the pros can't agree all the time on what's good and what's not. However, I think the 3DAudioinc.com listening test CDs, whatever their limitations, go a long way towards helping listeners be aware of differences and their own preferences.  I'm grateful for that.
Best wishes,
Mark H.