I just tested it out with MS Word and the variable fonts do not show up in the list of available fonts within Word.
Boo.
They should show up with their individual styles, but you can't variate them. They need to contain a STAT table to work on Windows though.
Hmm. Although it shows up in Illustrator, Photoshop and InDesign, it does not make an appearance in the MS Word font list, either as a master or as individual styles.
Adobe apps don't need a STAT afaik, Microsoft apps do.