Once you adapt to using a mirror, you won't ride without it - when I take a spin around the block to check my latest bike adjustment (or whatever) I may leave my helmet but not my glasses with the mirror! Most bikes seem pretty twitchy but I can still coast or lightly pedal with no hands, although not comfortably - e.g., I will roll my shoulders to loosen my muscles but I'm uncomfortable removing the top of my water bottle and drinking from the open bottle. But I think I will become more comfortable as I ride more. And it must be possible - the pros do it extensively and their bikes are undoubtedly very twitchy. (I'm only 64.)