I'm not getting into a mine is better than yours debate but here's a bunch of demo videos on the BK9. Most have been listed here already but here they are all in one place. Besides its just 16 lbs. Love that ! I'll soon have an upstairs studio so I'm really happy about the weight. And I've said many times the two screens give lots of real time info and the IPAD integration is also available. More info than I can use in a live situation.

http://www.personal-view.com/talks/discussion/6542/roland-bk-9-arranger/p1

For live performances I think its fine. For studio recording quality sounds maybe VSTs are better, or real instruments !
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Bill in SC --- Roland BK9 (2) Roland BK7M, Roland PK5 Pedals, Roland FP90, Roland CM30 (2), JBL Eon Ones (2) JBL 610 Monitor, Behringer Sub, EV mics, Apple iPad (2) Behringer DJ mixer