At the moment I think it's getting put down to me just being too picky ;-) People were saying that the edge unresponsiveness was due to overzealous accidental touch algorithms, so that could be software.
The rest of it is just me moaning or a dodgy unit but at the moment I'm picking up my s24u all the time because I know if I pick up the ip16pm I'm going to have to tap a few times, swipe a few times before it registers. (have tried complete reset back to factory, setup from clean, no screen protector, put accessibility responsiveness to max and so on). Just feels.... slow.