I'd be willing to try using an iPhone app onstage.
Really. SampleTank on an iOS device might be just like having any other keyboard-less synth in a rack, just more portable. I'd at least be open to the concept.
But I probably
won't be trying this. Two reasons: 1) it would require buying an iPad-sized unit and a stand to mount it on, at a cost of around $700, and 2) I doubt the reliability of such devices.
Got to buy an iPad or similar-sized Android device because running it on an iPhone, or my slightly-larger Galaxy S3, would be impractical. Imagine trying to select a patch in iSampleTank with your left hand while continuing to play with your right. I do this all the time with my hardware synths, but they're push-buttons. Even as a keyboard player I lack sufficient left-hand dexterity to operate a touchscreen interface left-handed while multi-tasking. Heck, I have a hard enough time on my Samsung phone using my right hand and no distractions!
I'd also have one more wall-wart to contend with, to find a wide-enough space on a power strip to plug it into, and one more cheap power supply to potentially fail in the middle of a gig. We've all had that experience with stompboxes. But I wouldn't dare run the thing on batteries. We've also all had the experience of having batteries run down in the middle of a set. For $700 I could get a real synthesizer that mounts in a rack and plugs into the same power source as everything else for proper grounding and minimal cable runs.
And speaking of cables, all of those devices have proprietary cables that are nowhere near as rugged as the signal cables we rely on for live performance. Those little cables have itty-bitty connectors and microscopic conductors. When they fail, you can only hope it's the cable itself (of course, you'll carry a spare!) and not the itty-bitty connector in the device itself. A speck of dirt is all it takes to make the device useless.
The most likely part of an iOS device to fail is the display. Repairing it costs as much as new unit. Without a working touchscreen, the device is a doorstop. The glass on my Samsung shattered the second day I had the phone. It cost $200 to replace, but only because I'd bought "insurance", else it would have been $600.
These devices are just not very rugged. My hardware devices that I use onstage are all built like Soviet tanks. They've been dropped, frozen, overheated, had drinks spilled on them and been banged on continuously for years -- and they still work. I've never had a cellphone go for more than a year or two before failing. I don't think they're made to last longer than that, on the presumption that you're going to replace them in a year's time.
And I'm just thinking of iStuff in terms of sound sources such as a sample library. Forget using an iPad as a recording rig. You can only view a half-dozen tracks, there is no phantom power, MIDI I/O, zero-latency monitoring, multiple inputs or outputs. Two 22" screens are barely adequate for my current setup - I wouldn't want to go back to a single 19" display, much less downgrade to an 8" screen.
iOS and Android devices are consumer products. Obsolescence is built in, and they are not intended for longterm use. Their features are chosen for the widest consumer appeal, such as kids who play games and grownups who watch
porn football. A TV show or Skype conversation does not require high-quality AD/DA conversion, so it's software-based. A little aliasing won't be noticed when you're listening to pop music on your Apple earbuds, so we don't sweat it. Frequency response? Of course it's 20-20KHz, says so right in the booklet that comes with it! Mmm, no.
OK, I'm ranting now. I've got issues with the whole thing. But don't tell me I'm a technophobe who's unwilling to try new things. And jeez, don't tell me my concerns are irrelevant because I'm old!