I am sitting at my computer trying to put into words just what the BK9 offers, and the simple answer is …
Everything! You can never really appreciate a keyboard from a review and in this case, it’s true. You have got to go and play one of these keyboards for yourself. I will try to help you by pointing out the great features that the keyboard has, but please pop to your local Roland dealer and try this keyboard for yourself. 
Features found on much bigger, more expensive keyboards are all on the BK9. 16 Track sequencer, 5 multi-effect engines and a whole host of connectivity options.

http://jazzhooves.com/?p=253

OS Update released

• Compatibility with BK-9 Performance editor. Copy performances. Now you can copy one, several or all Performances from one Performance list to another.
• Importing User Programs from G-/VA-/E-series.
• The DYNAMIC ARRANGER Function allows you to control the volume of the accompaniments parts depending on the way you strike the keys in the chord recognition area (velocity sensitivity). Mark&Jump function to variation 1-2-3-4- during the smf playing.
• User Drum Kit Added the possibility to edit some parameters that characterize the sound of a drum instrument.
• Fade IN/OUT Setting It is possible to set the Fade In and Fade Out time duration. These parameters can be selected using [MENU] button -> "Global"
• Bar Level Slider Assign (H.Bar Level) This parameter sets the "H.BAR Level" slider (Red slider) to adjust either the overall organ volume level or the overdrive level.
• Set the transpose to 0 in One Shot Now you can set the transpose to 0 immediately, press the [KEY] button while the display shows the "KEY" pop-up window.
• MIDI (Rx Common Exp) This parameter allows you to specify that Expression messages received on the channel you select here (1~16) should affect all of the BK-9's parts (except for the song parts). Selecting "Off" Expression messages should only affect the part that receives on the MIDI channel used by the Expression messages.
• Pedal Controller FC-7 . You can use the FC-7 footswitch unit Board to activate the Audio Phrases. The Audio Key function uses the 7 right most keys of BK-9's keyboard. If you want these keys available to play notes, you can assign the activation of the Audio Phrases to the optional FC-7 footswitch unit Board.
• Assign Switches (Unlock All function) You can to unlock in one shot all filters acting when changing performances.
• Scale Tune Switch The "Scale Tune" settings now can be applied to the Upper1 and Upper2 separately. Linking a MIDI Set to the Performance memory You can link a User MIDI set to the Performance memory.
• Performance Hold (New filters added) Three new filters "Assign Switches" and "DBeam" and "MIDI Set" were added.
• One Touch Hold (New filters added) Two new filters "Assign Switches" and "DBeam" were added.

http://www.roland.com/support/article/?q=downloads&p=BK-9&id=63052872