I have never used one, but i love my Peanut Shell cover. I cant remember how much i paid for it, but it was worth the cost. You dont have to keep lifting the cover to look at your baby...it has a little opening in the top you can look in.
I personally love my Udder Covers.....I purchased three to have one ready in my diaper bag, upstairs and downstairs. I use them when there are other people in the room. I am able to see my son as the opening in the top makes it easy to do so.