I think the dolls that you feed and they pee and poop are disgusting. I think the breastfeeding doll is pretty cool, though I don't know why a special doll is necessary, and I wouldn't buy it because I want my kids to have imagination, not a toy that needs batteries and talks/walks/etc.
When my second son was born, my oldest son (at only 3) would feed his stuffed animals like mom was feeding the baby. IT was adorable. My daughter was adopted at 3 from Ukraine, and she has babies but we tossed the doll bottles the one doll came with. We have friends who nurse their babies and that is how we feed babies. She doesn't lift her shirt but she will say 'I feed the baby' and hold the baby to her chest.
Why is it ok to give a baby/doll a piece of plastic, but not allow kids to do what is natural? There is nothing disgusting about breastfeeding, there is nothing disgusting about little kids feeding their dolls.