They let you get most of the matted up hair and excess fur out. We use a small pet grooming comb and a type of comb that a a friend of ours who is a professional groomer recommended that is built so the bristles swivel. For a preventative, feed papaya tablets like you buy at GNC or a comparable nutrition store. No, that is not necessary. We also don't recommend body piercing.
Most rabbits do look pretty darn good in an ear tatoo, though.
I have heard they can tolerate cold better. A- You are right on the money about rabbits being able to handle cold weather. They are built to handle this, particularly long-furred breeds. Heat is the biggest killer of rabbits. Our rabbitry is air conditioned and heated, so this isn't a huge worry for us.