I recently bought Factory for iOS (awesome synth!). I also have a Linnstrument 128 (http://www.rogerlinndesign.com/linnstrument.html).
The Linnstrument is a MIDI controller following the MPE (MIDI Polyphonic Expression) standard, but purportedly Sugar Bytes is not interested in MPE, too bad!
The Linnstrument implements a mode called "Channel per row", where each one of the eight rows becomes monophonic and emits notes on a different but static MIDI channel. That way the interaction becomes similar to a guitar (or rather, a Chapman Stick ).
I'm using apeMatrix (http://www.apesoft.it/apematrix/) as a mixer/AU controller to run eight instances of Factory at the same time, having each one of them listen on a different MIDI channel. As you can imagine, this is quite CPU intensive.
On my 5th generation iPad, when I load the "init" patch on all eight Factory instances, the CPU usage goes above 90%. However, if I set the patch to monophonic mode and the Filter Smooth to Modern (supposedly cheaper than Vintage), the usage goes down to a more workable 65%. I expect that number to go back up once I load a more interesting patch.