Yep, that's precisely what I was missing! Thanks!
Just in case anyone else runs into this issue, in PM Preferences under "When Writing IPTC/XMP" and "For Tiff-based RAW photos" the "Add Embedded IPTC4XMP" needs to be checked (that is, if you're using RAW).
For use with Adobe products, we really recommend using XMP sidecar files only. Embedding XMP can cause problems for some Adobe programs, especially Bridge.
-Kirk
