The OS update works very well: the sound is now overall cleaner and many instruments are different (better for the greatest part). A few sounds seem thinner, and I have read somewhere that this is due to the fact that in the old OS they were actually a layer of two or even three single sounds. That's the reason why they were so fat and rich (I am thinking especially of the Golden Trumpet or the Pop Tenor); now they are thinner, but you can always edit your sounds and save them as programs. That seems to be the reason why the SD1 now has up to 15 notes of polyphony more for the right hand.