Squeak,
I gave a report on the PSR550 when I got them in at my store. I was blown away at how much better the 550 is over the 540. Besides much improved styles, the sounds are much improved as well. It's not that there are that many new sounds, but all the sounds are vastly better. I was also impressed to see Arabic drums included and the style data base has been implemented from the PSR9000. Although the keyboard basically looks the same (except for the 4 color display), everyone who plays it, loves it!
George Kaye
Kaye's Music Scene