I have received my SK1 and I'm going to give you my 2 cents on it.
I use my gear for playing live. I own a Roland Fantom X7 that I use as my main keyboard (I love the Internal Sounds and Expansion Board capability, the Display size and how easy it is to layer and split the keyboard, not to mention its cutting sounds) and I wanted a second keyboard that would give me: #1 most important, the best sounding B3 Organ and Leslie. #2, great sounding Electric Pianos and Clavs. #3, a really good sounding Piano (as I don't use Piano that much, but when I do, the Roland does the job for me).
I also own a Nord Electro 3, a Nord Stage 2 Compact and a Kurzweil PC361 with a NEO Vent. Please note that I wanted a "Master" of a few sounds vs. a keyboard like the Kurzweil that had a ton, and I mean a ton of great sounds, that I didn't really need (not to mention how long it takes to scroll through and hear all the sounds the first time!).
So here we go!
1) The SK1 Organ sounds better/more realistic than anything I have. The best way to describe it is that it sounds like a "Hammond", whereas the Nord and Kurzweil sound like a Nord and a Kurzweil trying to sound like a Hammond. Obviously the Nord and the Kurzweil sound great, but not like a "Hammond".
2) The SK1 Leslie gives the Vent (which sounds even better than the new Leslie model on the Stage 2) a serious challenge. So close in fact, that I have already sold the Vent, as there's not a $450.00 difference in the sound, if any.
3) The Electric Pianos/Clavs on the SK1 sound as good as the Nord or Kurzweil ones.
4) The SK1 Pianos sound great when playing along with Guitars, Bass, Drums, etc.
5) Action wise, the SK1 feels just right to me, as it is a little stiff (similar to the NE3 and Stage 2), relatively speaking, and I prefer that to the synth action of the PC361.
6) I can split/layer the SK1 into 2 zones, with one of the zones always having to be a Organ, but that's what I wanted in the first place. You can split/layer the Stage 2 infinitely more, but remember that I told you why I wanted a second keyboard to go along with my Fantom X7. The Stage 2 is capable of far more splitting/layering than the SK1, but it exceeds what I need for my second keyboard (not to mention the $1000.00 + difference in price between it and the SK1).
7) The SK1 weighs about 16 lbs., and if you gig regularly, you can appreciate that fact!
I won't even get into how deep the SK1 can be edited (as in the different model B3's and Leslies, etc.). I'm just talking about the Factory Sounds as they come on the keyboard.
Now I know the Nord Electro 4D is about to come out and that it has the newest B3 and Leslie Models (like the Nord C2D has), but I'm willing to bet that it will still sound like a Nord (not bad, btw) and I'm happy settling with and owning a Hammond! Plus, the NE4D can't be split or layered.
IMHO, Nord should have called it a Nord Electro 3D, as besides the addition of the drawbars and new Engines, it still is mainly a updated/newer version Nord Electro 3 (even though I find it interesting that the NE4D will have a better Organ/Leslie than the flagship Nord Stage 2).