Very quickly - If you are a styles player and go gaga over SA and other sounds, then this s910 is worth the step up. If you are mostly a piano/organ/strings guy, then maybe not; those sounds are pretty much the same since the 3000, IMO.
After sitting down with the 910 for just a half hour, I'm impressed with what I hear in the upgraded styles and the instruments used in them. I will probably try to use more styles now vs SMF. I don't normally use the OTS feature, but the sounds here were much better paired with the particular styles. I like the Warm Grand over the default grand piano. That's about it for now. I've barely touched the surface of this new machine, but I can see there lots of other new features to explore. I wasn't planning on upgrading, but the buy/sell arrangements were deals I couldn't pass up. I think I made the right choice.