Addy's physical therapist wants her to work on playing with her feet (reaching for them, grabbing them, and even sucking on them). So far this seems to rank only slightly higher than tummy time on the "List of Things Addy Likes to Do." It doesn't make her mad like tummy time does. She just doesn't really seem to care that she has feet.
PT did caution me that another client of hers who has Spina Bifida accidentally used her toes for teething...