My S88 Mk2 arrived yesterday. I have both the original S88 and the new Mk2 side by side, so I can compare them.
One thing I think people need to realize is that there's a break-in period with these keyboards. I haven't been inside an S88 yet, but having been inside other similar keyboard actions, I've noticed that they put a lot of silicone grease on the action parts. I think this really contributes to the "spongy" and viscous feeling that these keyboards have out of the box. OTOH, I've never noticed that on the weighted Korg Kronos keyboard, Yamaha Motifs, or the Kawai VPC1 (all much better actions, IMO).
My original S88 got gentle studio use, only, so it's in excellent condition. Comparing it the the Mk2, the original version seems a bit faster, but also somewhat noisier. But, comparing the note on the extreme hi and low sides of the keyboard (which don't get played as much, and perhaps are not as "broken-in"), the extreme hi and low notes of the original version feel a lot more like the new Mk2 version. So, I really wonder if it's not, in fact, the same Fatar keyboard action in both the new and old S88. If it's different, I don't think it's a lot different. For the moment, I think I prefer the new Mk2 feel, and I think it'll be better after it's been used awhile. It's nowhere near as good, though, as my Kawai VPC1, Kronos or Motif. Those actions are clearly superior. But, IMO, the features on the S88 Mk2 that interface with my DAW and NI instruments make it worth it. In my studio, I have the S88 Mk2 in front of me, and the VPC1 to my left, for when I need to do serious playing. It would really be nice to have a VPC1 quality action in the S88, but we didn't get that. It would be great if NI picked a different action supplier other than Fatar the next time around.
Here are some other things I noticed about the new S88...
1.) I would have thought that the construction would have been similar with just the added screen features, but it appears that NI really did a big re-design of the case (probably to save money). The original case has more metal, and seems to weigh more. The front and back edges of the original are also about 1/4" bigger. The Mk2 does not have end bells. The top part of the Mk2 case is a big one-piece plastic casting. Probably won't make much difference in studio use, but I think the new Mk2 would be more prone to breakage on the road. The original version has end bells with some kind of rubberized padding. If you bashed the end of the old version, you could easily just replace an end bell. Bash the end of the Mk2, and you're going to need a whole new top part of the case. The edges of the new version are also crisply squared off. Looks nice, but more prone to breakage. On the plus side, the connectors are recessed on the Mk2. I also think the Mk2 is easier to grab and pick up since it has sort of a pedestal.
2.) I do like the newer, smaller LED lights on the keyboard. Makes the Mk2 look less like one of those Magic Fingers organs from the seventies.
3.) I like the fact that they went to wheels for pitch bend and modulation, plus an additional touch strip. The wheels feel okay, BUT, they are definitely not at the quality level of those, say, on a Yamaha Motif. The S88 Mk2 wheels feel kind of cheap. They also have kid of a viscous damped feel. Probably a lot of lubricant in those pots, too. Might be faster after they break in. There's also a bit of mechanical scrunch in the modulation wheel (might just be my unit).
4.) I DO like the fact that they made the two pedal inputs similar. Now, they can both support continuous controllers as an option, so you can use both a volume pedal and a continuous sustain pedal (great for piano damper pedals in virtual instruments that respond to continuous control). Also, there are number of parameter selections for configuring the pedal inputs (you need to click the MIDI icon on the stand-alone version of Komplete Kontrol to do this). I'm thinking it's possible that the new Mk2 might work with a wider variety of third party pedals.
5.) The new screens look very nice. Not sure if that's going to change my life, though. I have my big computer monitors right in front of me, so I'll probably continue to do my instrument selection on them.
6.) The feel of the buttons, pots and rotary controllers on the new Mk2 feel the same as the old ones.
So all in all, I think I'm glad I made the switch. NI did not hit it out of the park with the new MK2, but there are some improvements. It'll be interesting to see what the keyboard is like after some break-in. I hope it doesn't get noisier.