Their barbs are manicured...they will not hurt you. A rays barb grows like our fingernails, so they are not 'barb-free', but the barbs are trimmed on a regular basis such that you are in no danger.
We did this a couple weeks ago and it was fun, if not a little creepy with those huge rays swimming around your legs, brushing up against you. My 6 y.o. enjoyed feeding them, though she claims one bit her, which is not possible because they don't have any teeth.
I found the 'pre-show' where they tell you about rays in general and the rays at CC in particular to be very informative and interesting.
Will certainly do the experience again if I find myself back at CC.