Thanks Harry and Dusty!
The NDS arrived last Saturday morning -- perfect timing as the weather turned bad starting Saturday night, with a foot of heavy, wet snow to follow...
Opening the box, I had two initial impressions: it's a surprisingly heavy component (compared to the NDX), and the finish of the casework is superb (a very nice step up from my early-version NDX). Learned from my dealer that a lot of the NDS's weight is in the spring-supported brass boards. Once the transit bolts were removed, the NDS does feel extremely wobbly! I took great care when picking it up so as to not have the boards bump into the sides of the case. Fortunately, the NDS has hard plastic feet instead of rubber, which made it a lot easier to place onto the Fraim's glass shelf (once two feet were down, I could slide the NDS back into position). Also learned from my dealer that Naim has now outsourced the casework finishing to a new supplier in Switzerland. Good move IMO -- this new supplier obviously knows what they are doing. By comparison, the NDX and DAC's finish feels a bit rough. In fact, on first glance, I mistakenly thought the NDS case was all brushed aluminum (like the 500 series), but touching it revealed that it was indeed powder coated.
Once placed, I ran through the now familiar setup menus, and made sure everything functioned well (which it did). I listened only very briefly -- just a couple of minutes. My initial reaction was that it sounded surprisingly good -- maybe a little shut in at the top, and little shy at the bottom. One other thing I noted was that, unlike the DAC (and to a slightly lesser extent the NDX), there was none of that initial hardness or edginess that I was expecting. But knowing that listening right out of the box is pointless, I tuned in to Radio Paradise, put my speakers on mute, and let it run for 12 hours.
Late Saturday night, just as the snow was starting to come down in earnest, I gave the NDS a first listen, and was very pleasantly surprised. The initial hesitancy was gone (!), and I could now hear good extension at both frequency extremes. I could pretty much immediately understand why you NDS owners were saying that it had a more "analog" sound than other Naim digital players. I too heard a richness in tone that I normally only associate with vinyl. Oh my, what a beautiful sound! Had it really only been running in for half a day? I was so impressed! I was also shocked to look at my iPad to see that it was now 3am...where did the last 4 hours go? How surreal...
Have had three wonderful evenings of all digital playback since then, and the NDS is sounding extremely good to my ears. Am trying very hard not to gush about its sound quality, as I expect it at some point to do the old roller coaster thing...but it just hasn't happened yet! I can say that, IME, the NDS has sounded more right on first listen than any other Naim product I have ever owned. It has made me wonder if Naim was now making more of an effort to burn these in? I was prepared for the NDS to sound ok...but not great! And for these first few days, it has indeed sounded great!
I will try and develop more thoughtful comments on its sound quality as the weeks go by. But suffice it say for now that it is the best sounding digital component I have ever heard. The NDX->DAC had set the bar pretty high, but IMO, the NDS is clearly the better player for me. Right now, I do realize that my reactions are emotional, and fueled by a new pride of ownership. But I do also believe that the NDX->DAC is very impressive...just in a different way. My feeling is that the NDX->DAC delivers a more "technical" sound. It gives great detail and energy, but I think the NDS has got more...soul. To my ears, the NDS sounds more involving -- more effortless -- more natural -- more real. I feel like I was quickly and unexpectedly drawn into the NDS's huge sound field -- time collapsed, hours passed, and I felt completely connected to the music. While I enjoyed owning the NDX/DAC, I must admit that I would often catch myself thinking of spinning records instead. My vinyl setup has always had a wonderful emotional effect on me...but only for 20 minutes at a time. Getting into that same "zone" for an hour or two at time with the NDS is a new, and wonderful experience. I am convinced that I have found my long-term digital player, and I am planning on buying a lot more used CD's!
More later, as I still have the 552PS and 555PS DR upgrades left to go! 
Hook