Ian, the BK-9 is priced competitively although the two small monochrome LCD screens are a deal breaker for me. You can only view one screen at a time and since I'm not a chameleon (able to view both screens at once) it's probably difficult to navigate the menus and kind of like playing game of ping pong only with your eyeballs. Back and forth, back and forth, back and forth and I can imagine playing the BK-9 live would be a chore because your attention is divided. Plus I don't like the fact you need an iPad to view things in color. Other than that it seems to be a decent arranger although I've read some user reviews that say a lot of the sounds are rather mediocre. But at least Roland is back in the game and for that I give them credit.
Casio has done some amazing things recently and they're still able to keep prices relatively low compared to the competition. Remember the MZ-2000? It was a good effort by Casio and it was also considered a higher-end arranger at the time. But it only had 64 note polyphony and that is still true today with the WK-7600. If Casio doubles the polyphony on its new arranger(s) more people would be persuaded to check out Casio in my opinion. They are losing the "toy" image and it won't be long before they give Yammie, Roland and Korg a real run for their money if you ask me. Yamaha may dismiss Casio but they do so at their own peril in my opinion.
Nigel is right on. Casio is becoming more cutting edge and it seems with each new release they're giving more features and even better sounds. What's not to like?

Beemer, Yamaha is charging $5,499 for the 76 key Tyros 5 and with tax (8% - in California) it ends up being $5,938. But in my opinion the Tyros 5 is only worth about $3,000 when you get right down to it. The Tyros 5 doesn't have a sampler and they only gave it 128 note polyphony (Tyros 4 users complained of note cut off by the way) and there is also no micro-editing and the B3 organs are kind of cheesy and Yamaha charges you extra for additional storage. I'm sure there are other shortcomings but overall it's a great sounding arranger for the most part but it obviously costs and arm and a leg. If people keep shelling out then Yammie will no doubt keep charging an arm and a leg until people wise up.
I like a lot of the products from Yamaha as I've stated previously but greed has gotten the best of Yammie when it comes to the Tyros line in my opinion. I say that with a sad heart because overall I think Yamaha is a great company for the most part. Although the executives at Yamaha Japan possibly consider me 'public enemy number one' because I'm not afraid to speak my mind about things I consider shortcomings or just plain wrong. But I also do that with Korg, Roland, Ketron and even Casio if I feel they deserve it. In other words, I don't discriminate or place one above the other like some fan-boys have a tendency to do. I won't name names obviously.
If people like a certain product then more power to them. But I've learned if you become too attached to a particular company you're usually in for a rude awakening at some point because a company's number one priority is mainly their own bottom line and the customer in many cases is way down on the totem pole in the scheme of things unfortunately. It's better to take an objective stance and in so doing end up with the best product for your own needs.
All the best, Mike