I'm not a sheet reader on the gig, and what lyrics assistance I need I can use a text file on my G70's display, so I haven't felt the burning need to use an iPad yet.
In many ways, I'm really holding out for another generation of these things. Their inability to do more than one thing at a time is a bit disappointing given how much they can do.
As I've alluded to in other posts, for what an iPad app could do that I could REALLY use, these apps don't cover it. About the only thing these do that seriously tempts me is the much easier Performance list editing and creation, and the keyboard letter input, to speed up naming and renaming. But, in fairness, there isn't anything that these do that you can't do any other way (other than the 'Favorite Tones' feature for the BK7m), so banging down $700 or so (not much point in one of these without the cellular option) just for that, or a more convenient .pdf reader seems a bit steep.
We are already seeing dual form tablets and laptops on the PC side. These seem to be a far more practical option, and I doubt Apple will resist them too long. I can wait...
If Roland offered a full featured editor for the BK's, then yes, it might be a more instant buy. But as you all know, given that I am still happily making music on my paleolithic G70, I am not exactly an impulse buyer, and like to extract the maximum value and familiarity with my gear. When they make something I HAVE to have, I'll get it. In the meantime, I can wait!
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An arranger is just a tool. What matters is what you build with it..!