I have not owned any SN AP products, just the EP ARX2. I thought the FP-7F demo on the website sounded horrible, but did find a NX demo on YouTube that sounded very good. I think editing sounds makes a big difference, as Rolannd doesn't seem to have such great settings out of the box. I was at GC yesterday checking out the GFX, but the keyboard was so disgustingly grimy, I really didn't want to play it. Plus I didn't have headphones and it was extremely noisy in there.
Personally I find the Roland layout and designs to be dated and genereic in aesthetic design. The G8 was a light show atrocity and the 700NX series doesn't look much diferent from the SX. I really don't like the layout of the editing functions of the 700 series, but I could probablly live with that if it really had what I wanted from a sound and action perspective. Their stuff does have excellent build quality.
At this point, I am more focused on EP sounds, because when I want to play AP I most often play my Shigeru. The EPs on the CP1 are amazing, but the MP10 has me interested. The 700NX has me interested on the AP side but I already had my time with the SN EPs.
My 2 ownership experiences with Roland (700SX and G8) haven't left me with such a great impression of Roland sounds or product design.
Have you had much time to spend on the RD700GXF/RD700NX? Both are in an entirely different universe than the RD700SX or G8 IMHO. Both sound and play much better and as for design, I think the RD700 series is nearly idiot proof. The layout is very intuitive and easy to use, and build quality is top notch. I am admittedly biased since I own the GXF and temporarily owned the NX.
Like others have said, it really is going to come down to what you like and what you want to use it for. I just recorded playing and singing "Give Me The Simple Life" on the Motif XS8 and was terribly disappointed with both the sound and action. It sounded like my Yamaha P80, and felt worse action wise. It has some terrific EP sounds and Organ sounds, but as a piano, it sucked. I suppose most guys who buy that don't buy it for a piano though.