The lower pulley (tension pulley) on many of the Shimano Ultegra ders does, in fact, have a balled bearing. It's easy to peel off the two seals, flush and relube with grease. IIRC the DA lower pulley, of the same vintage as the Ultegras, also is balled. As the lower pulley doesn't need any float it's a simple application.

Now that I have thought about this a bit I do remember that some Shimano upper (guide) pulleys use balls. DA IIRC. Two rows of balls held in a plastic ring and run on a cylindrical center shaft. Wish I could remember more detail. Andy.

http://www.sicklines.com/tech-info/xtr/XTR6N.jpg
http://i224.photobucket.com/albums/d...07partlist.jpg