When I was first learning (listening to Greg Rolie, Bill Payne, Keith Emerson, Rick Wakeman) , it seems it was really rare for someone to play in the flats, at least the way I remember it. I think you have better fingering cues with the black keys. Personally I don't like playing in B. When I'm just jamming around with myself, I'm usually playing a lot in Eb. Forcing yourself to learn in multiple keys is absolutely good for you. Give me charts in roman notation and I'm much happier.
I saw on an earlier post about using the transpose function assigned to switches in the Tone Adjust mode but I'm such a novice with this board at the moment I have to go learn what that mode is first..
