Just as a heads up, they didn't change the fill behaviour from the Tyros to the Genos. It's always been where if you don't hit it exactly at beat 1, it will sound different because the beginning of the fill gets skipped.
However, some styles take this into account, and the first 2 beats of the fill actually replicate the same as their main pattern counterpart (look at 80sPowerRock fill in C) so perhaps that's what you were remembering; some styles are much more lenient about when you press the fill/break. Some breaks, with everything on the 1st beat, then 3 empty beats? Very unforgiving!
They also didn't change the durability of the buttons; I've had several Tyros customers who've had to get their buttons replaced (under warranty, fortunately). Another forum member hit the nail on the head: pressing on the top half of the buttons tends to break them, but the button 1/3 doesn't, since that's where the actual give is (hinge is on top). But they sure changed the quality of the finish: Yes, the Tyros could lose silver paint around commonly touched areas, but you could always re-paint if you had an airbrush. The Genos, being just a molded plastic casing; once it becomes glossy from wear, it's nigh impossible to fix (short of spraying the entire chassis)
Mark