I cook it on low and have never experienced rubbery.
It's a little drier than if I sauteed or grilled it, but I always shred it up and let it absorb the cooking liquid. (I try to shred it at least an hour before eating depending on what our schedule is) My family loves this one chicken recipe with soy sauce and lime juice. I zest the limes and save the zest in the fridge to sprinkle over the food right before we eat it so it has a fresher taste than if it were all just thrown in the crock pot.
I will also use the crock pot to cook up chicken with mexican spices. I package up the extra shredded chicken and freeze. I always have a few bags I can grab for a quick meal of tacos/quesadillas/enchilladas.
