Just swap my Yamaha PSR1000 with KORG PA80 with a good friend and do some evaluation.

I was surprised that the fill-in button does NOT advance the variation to the next variation. This is a very typical use of the fill-ins. Granted that sometimes you just want to fill without advancing but it is quite rare and I can always hit the variation button to switch back. Also, because of this some of the fill-in seemed to be mismatched with the variation style.

With KORG i30, you can program the fill-in button to advance or reverse the variation style. With Yamaha, there is a button that allows automatic fill-ins when the variation button is pushed and selects the appropriate fill-in based on your next variation and the previous variation.

Am I missing something ?

Not only that. But the registration memory is awkward to use. I have to press 2 buttons: first the bank and one of the buttons near the screen to select a registration.

lukitoh,
You are missing something on the PA you can go into the style play menu and do several cool things with the fills.
advance 1>2 1>3 1>4 or visa versa. You can stay on the same fill.

Also there is a setting the last page (25 or so) that has a velocity setting, so you can prgram there that when you hit a key harder, it will advance to next variation or stop the accmp. and just play the percussion etc. Or do a fill. Also, if you hit anny of the fills buttons 2x's in a row, it will stay on the fill until you hit the button again, great thing for a longer fill. These are actually very cool PA features of the fills.
Terry