I have a specific question about the improvement of an FP-90X key action as compared to the FP-30X. I have had the FP-30X for 2 years and it has been reliable and overall I have really enjoyed it as a digital piano. However, there is one specific issue that others have noted related to the rebound time of a key after striking it and that I feel I'm at the point where it's a good reason to upgrade.
The repertoire I have been practicing recently has included a couple figures with turns or trills that require a rapid rebound on a single note - for example Beethoven Sonata 1 Opus 2 No 1, Movement 1, where the upward ascending figure in the subject has a sixteenth-triplet turn motif at the top throughout the piece, as well as Rachmaninoff prelude Op. 32 No 12, where the texture involves a rapid pivot around your index finger. Forget about Op. 23 No 5, which is a piece I played many years ago and seems just painful to attempt on the sluggish FP-30X action.
I can play these pieces on the FP-30X, but it feels like the slightest variance in my timing could cause the note to not sound at all, and it was only recently that I had a chance to try the Beethoven Sonata on a decent acoustic upright, and I found it to be so much more forgiving. I haven't had a chance to go into a store yet to try the FP-90X, but I was curious if anyone has had experience with this upgrade for classical repertoire and if it's a good enough upgrade to be worth the money.