I just received my Kurzweil SP2X yesterday (got rid of my PC1SE as the 76 note range was actually not enough for all my VSL keyswitch patches).
User Interface- A little more cryptic than the PC1SE because of the LED displat compared to the alpha-numeric one on the PC1SE. But otherwise, the interface is pretty quick to pick up and navigate through. I love the fact that controller assignments to the 4 knobs remains regardless of whether you're in patch mode or combi mode. Sooo much easier to assign controllers to the knobs too.
Sounds- Only comes with 64 sounds but they are excellent ones. Good representation of strings, pianos, EPS, organs and basses.
Keyboard- EXCELLENT feel. 7 variations of touch sensitivity make it perfect for any player regardless of their playing style. Keyboard is quieter than the PC1SE and has a little more bounce to the keys with a softer bed. Less "thunk" sound. It's a pure delight to play. Cons- no aftertouch.
Controller Features- I primarily bought this as a controller for my soft synths and it does a great job. For really quick passages I still rely on my Axiom 25 which does have aftertouch too.
Price- Well, the place I traded my PC1SE at gave me money back on this beast so I can hardly complain. I think it's $1250 up here in Canada.
Verdict- The best 88 note board I've played to date. Encompasses everything I need in a controller and a stage piano.
I've also owned the following 88 note boards for comparison:
Did you happen to try the Yamaha S90es? I trying all the keyboards I could find about 6 months ago and this one was the one I loved the best. It had the most "piano" feel to me of all of them, had separate mod and pitchbend wheels (what is it with Roland and the others, I know a joystick might be a little easier for live, but SO many libraries need mod wheel control now), and yet even with the piano touch, it still has aftertouch.
I forgot- I owned a Yamaha S90 as well. Too heavy that action was. For piano fine. For everything else, not.