I don't know if this counts but the latest Adobe Annual Report claims to be set in 'Myriad Master', which ia assume is a typo.

Si

That was a bit of a cheeky answer so here's a serious one. Myriad Pro would likely be of most interest to magazine publishers using InDesign, so the best place to start would probably be the magazine publishers lining up behind InDesign - there's a list of 'customer stories' at the bottom of this page... http://www.adobe.com/products/indesign/customerstories.html and go from there.

In the U.S., Health magazine uses Myriad.

http://www.health.com/health/

Creativity magazine uses Myriad, I do believe.

http://www.adcritic.com/