Possible Advantages:
1. Keeps Animals, especially Raccoons and Birds, from setting up home in your chimney or fireplace.
2. Keeps Rain and moisture from building up inside chimney. This can help reduce the chimney smell that often invades homes in the warmer weather.
3. Sheds ice and rain from the chimney crown, which is the cement cover on the top of the chimney structure. This will extend the life of the crown and eliminate some causes of cracking of the flue tile.
4. Increase draft of chimney, especially in areas with constant wind.
not totally necessary but it may save you on costs and aggravation later on
There is a lot of info on the web about them. I don't think they always help with back drafts. There are some specific models that are supposed to be better. Mine is not a standard top so buying off the shelf wouldn't work so a chimmney sweeper is the best bet. One of the things I remember when researching was keeping heavy rains out which can damage the masonry.
Just another reason to strap on the korkers. Got mine at HD for about $25 and it does reduce the cabin smell in the humid weather. Just don't let your kids see you locking Santa out.