Raimo, the 'hold' switch is for when you hand the camera to someone else and don't want them to change its settings (inadvertently or otherwise). It's rarely used, but handy when you need it.
For the record, I really like the MZ-S 'user interface'. I see why Cameron finds changing the aperture occasionally fiddly, but to me it's a very minor quirk on an excellent camera that is very pleasant and effective to use. Pat White
