I went to a big music store where they had a lot Roland: the FP-4F (Black), the 300NX, the F-120, and the 700NX to name those that are part of my observation about the Ivory Feel-G action.
From what I understood, the 300NX has the same Ivory Feel-G as the 4F and the F-120, the 700NX has the superior III-action (whatever it's called).
The thing is, the 4F felt more responsive/faster than my 4F. I compared the 4F there with the 300NX, and the 300NX was more like how my 4F feels. I tried it with headphones, without headphone, and without sound. I compared it with the F-120, too, which felt similar to the 300NX.
Back some months ago, I played a F-120 in another shop and had the feeling that it was lighter/more responsive than mine. So I'm wondering if there has been a somewhat of an upgrade or something to the Ivory Feel-G technology.
Now, I'm quite used to the action, though it always feels like a bit of a handicap. But for a beginner, it might be for the better, as I need to be very controlled and precise to be on spot with my sound and my rhythm.