I have had the Sx900 for a few days now and have it setup to my liking.
I used the 'Robinez' master EQ settings with some gain reduced at the top and bottom ends by a couple of dBs.
To my ears the sound is brighter and has better clarity.
The keybed has improved. No more noises from the keys!
The touch display is a great improvement and makes finding registrations, saving files easier and quicker.
If anyone is thinking of upgrading I wouldn't hesitate.