Pros: easy for baby to latch on to
Cons: compromises milk supply if used alone
My daughter was born over a month premature and had a horrible time getting the hang of breastfeeding. We tried everything to ease her into it, and even the lactation consultant was at a loss until we tried the Medela nipple shield.
Using the shield, my baby was immediately able to latch onto my gigantic nipples with her tiny mouth. It sure did beat pumping my milk and bottle feeding her and seemed to cut down on the nipple confusion that my little one was experiencing. It did take some time to wean her from using the shield, but that just took a little patience. You also must keep in mind that using a nipple shield exclusively for long periods can cause a reduction in the amount of milk you produce, so I found it helpful to use the nipple shield for only the first couple minutes of nursing and then letting her nurse without the shield for the remainder. The other alternative is to pump a bit after each feeding to keep the supply up.
Overall, I found the Medela Nipple Shield to be a very helpful and effective.