I use them on all my pipes. I don't want any teeth marks on the stem. I find them easy to use and very durable. They also make it comfortable and stable in the clench.
Growing up, I loved going in to Paul's Pipe Shop to pick-up something for my Dad... I think that has stuck with me all these years and is one reason I love this hobby.
My Current favs:
-Cult Blood Red Moon - currently available at Pipes & Cigars
-Lamb with Jam - Available at Country Squire
-Hobbit's Weed - Arlington Pipe & Cigar Lounge
-Lane Very Cherry - tobaccopipes.com or anywhere
-Vauen Auenland The Shire - tobaccopipes.com