I'm in the middle of trying to figure out how to replace the (very reliable, well-proven, cheap) push buttons on the front panel with a touch interface (a bit flaky, not widely used, but still cheap as no buttons are required) that uses Microchip's "Charge Time Measurement Unit" (CTMU) that is built into the PIC18F25K50 chip.

Initital testing (using Kapton tape as the dielectric) shows that it is feasible, but when I swapped the Kapton tape with 2 mm Lexan (polycarbonate) the whole thing turned to brown-colored stuff...switching became erratic and sometimes not responsive to touch. One of the problems is how to calibrate the sensing so that different finger types (big, little, sweaty, dry etc) work reliably and environmental variations over time (humidity, temperature etc) are accounted for.

Another problem is that testing is a little difficult because it's looking like I might need to have a prototype board manufactured, then tweaked, then re-manufactured and so on. That could get expensive.

Still, I think it is worth persuing if only because the unit would look better with a flat panel interface. One of the good things about using CTMU intead of buttons is that the front panel artwork is simply printed on a piece of paper and slipped behind a transparent polycarbonate sheet - no more drilling holes or wiring switches. Your front panel can be printed on an inkjet printer so you can make it look as classy or weird as you want.