Hello,
This weekend I went to two big dealers for Roland and I asked specificaly for Kf-90 but they do not have it. In fact, the sales people have not even heard of it! When I told them it is a new keyboard, they said, "OH that's why". I regret that I do not live by George Kay store, otherwise, you would find me there every weekend.
So what I could do is I went to the Roland homepage and looked at the specification of that keyboard:
Here is the similarities:
1) weighted 88 keys.
But that is where the similarities end.
It seems to me that the Kf-90 is more of the class of "portable clavinova". It is closer to Yamaha P80/P200 but with some styles.
Sk880: is actually a WK6 with 88-keys (to borrow George Kay description). Although I like the Sk880 way better than the WK6. Maybe my ears need some checking.
SK880 has a powerful dedicated sequencer, good synth, dedicated auto-accompaniment and style factory, wonderful workstation/arranger.
KF-90 has some styles, some sounds and some basic features but that is it.
So clearly we are comparing apples with oranges.
Here are some of the questions I have about Kf-90:
1) How does the acoustic grand piano sound in the KF-90?
2) What about the styles? (you do not need to many styles, but the keyboard has few and if you cannot load new ones, nor make new ones, the styles better be excellent and cover all your needs)
3) what about the other sounds? the strings, the violin, the flute,...?
4) what about the other features?
For yourself,
1) Do you really need a synth? It is nice to have but will you ever use it?
2) Do you need a dedicated sequencer?
3) How about other options?