I first added aerobars to a touring bike 13 years ago, and I would not consider doing without them. As others have said, they are not for times when you need quick access to the brakes, but they are perfect for riding on quiet country roads, climbing steep hills, and resting the hands (because you do not need to grip aerobars.)
I have Profile Airstrykes. The padded cups are spring-loaded, so you don't lose a riding position that you do with non-spring loaded cups. Some people find they rattle, but I haven't noticed.
http://www.profile-design.com/2006_p...airstryke.html