The E-A7 looks bewildering... I'm surprised Fran thinks the UI is better than the BK-9. I had a BK-5 briefly, and compared to the Prelude/GW-8, controls are laid out pretty thoughtfully for a real-time arranger. Not giving up my E-50 just yet though... :-)
Although it does indeed look difficult, E-A7 has the best interface of any arranger I've used and I've had several. If Roland would put out a new E-A7-like arranger with a large touch screen and jog wheel, they would have a winner, although I might not switch since I have so much time invested in my PA900 now.