Do they use an actual touch sensors, wafer buttons, or a light matrix? The latter are more reliable.
Not all skin reacts well with touch sensors. I had to take on an assistant just to press buttons as the tech changed on cash registers I used to repair.
Phones without buttons are just becoming tolerably usuable for me.
Neat, but nothing is as reliable as a mechanical switch. Touch sensors trigger on me from 4-5" away one day, and have me tapping like a woodpecker the next with little response. We called the phenomenon "Highlander finger" or "crap" among other things if it was on a Monday 
