I was against Apple for a long time until Roland more or less forced me to consider an iPad in order to control my Integra conveniently.
Meanwhile, the iPad is extremely useful to control my new SD 1000, which has no buttons. There are two fantastic apps called Set List Maker (with midi functions) and iMidiPatchbay, which works like a hardware patchbay. I'm especially happy with the latter, you can turn a simple keyboard into a split or layer keyboard addressing different sounds of the Ketron module, you can route midi signals, you can send bank/program change messages to change sounds pressing a single button, or transpose easily. No, it is not a simple non-serious gadget like some smartphone apps, it is a very serious tool.