I think everyone has sensitive breasts, lol. It was a little uncomfortable for the first week or two but not painful. If there is actual pain that indicates that something needs correcting (bad latch, tongue tie, etc). They don't sleep longer but I co-sleep and breastfeed and I've never been sleep deprived with a newborn. They squirm, you wake up and put a nipple in their mouth, then you both go back to sleep. It's convenient. It's cheap. It's healthier for you and the baby. There are many women who switch to formula because they run into breastfeeding problems that they don't know how to fix or are misinformed about breastfeeding. If you want to do it I would recommend getting a book or reading up about it online for free. http://kellymom.com/
is a great place for breastfeeding info.