eugeniusz:
dc42, as a hardware user, I don't like to enter menus just to adjust speaker volume or something. And same about buttons - dials are more informative and quick to set. Apart of my preferences, system with "old style" controls will be elder friendly.
Fair enough, however I didn't say anything about menus. Why not use a 128x64 GLCD for the display, then you can display the set points and actual temperatures all the time? If you use potentiometers and don't display the set points, then you'll have to calibrate the dials on the potentiometers.
Rotary encoders are elder-friendly, you can make 1 click = half a degree, or whatever other increment you want.