I spent some time with the bk-5 at home, but I assumed I can use it same way as bk-7m that is I can plug in my keyboard and use its arranger... I assumed I have it as cheaper and finally updated BK-7m....well, not so. The BK-5 will not trigger the arranger over external midi keyboard... or maybe it is just me? I tried everything, it will play all the 16 channels like a module but never trigger the arranger no matter what I tried to set up.
Anyhow, for the money it is pretty good board, with plenty of nice styles.
I was first pretty disappointed by the sound - the speakers are just wrong! Compare it to PSRs it played like a radio. Plugged my senheiser 598 headphones and the sound was all muffled, like if you listening to piano on a cheap board and the high harmonics were missing...

Then I pluged it to speaker system and got a lot of fun hours out of it. It sounded pretty good actually on PA. Didn't like the pianos and strings but the brass and winds are pretty good on those rolands!
The styles are also interesting bag, I listened to some youtube videos before and they sounded like overarranged midi files, but hands on (or speakers on) I was actually pretty pleased with many of them. They give pretty good "live" vibe. I have PSR910 and you can easily recognize the PSR sound with closed eyes but some of the roland styles (jazzy) were a breath of fresh air! I think maybe the roland simply needs to play live on PA (hence the disappointed youtube videos - it is too quiet)

At the end I ended up returning it as I couldn't make it work as a "module" and I didn't care much about the keyboard itself. Still thinking about bk-7m.... but are they ever going to update the firmware or the bk-5 is the "firmware update"?

Anyway for the $1k it is pretty good board I think. Lot of fun for sure!!! I don't know why my headphones didn't like the BK-5...
It isn't PSR910, but I don't think it is meant to be one, rather like some lower priced PSR.
Not sure about the speakers... I definitelly didn't like them..but..

One thing: I really think they SHOULD have midi sequencer or at least chord sequencer in the BK's. The audio recording is just too "nothing", an ipod with some simple multitrack would do a better job I guess, maybe they should just add an ipod dock connector...

Anyway, interesting key this Bk-5. Maybe too little, too late would be my total impression. With yamaha putting kitchen sink in PSRs maybe roland can step up in the game... like the chord sequencer which is sort of staple feature in arrangers - even the microarranger has it for half the price.