Ultimate Ears is a made-to-order in-ear headphone company that teamed up with Logitech in 2008 to offer high-quality, high-end gear designed for the working musician and anyone else who wants a perfectly snug pair of earphones.
The key to higher-end versions of Ultimate Ears (such as the UE7) is the fact that each pair is custom made from an impression taken of each customer by a qualified audiologist. Once the impressions are complete they must be sent to Ultimate Ears so that production of the earphones can begin.
As for who is using Ultimate Ears? It would be easier to list the famous artists that aren't using them. Everyone from Aerosmith, AFI and Air Supply down to Wynonna, Xzibit and ZZ Top wear Ultimate Ears on stage and in the studio.