The latest version of iView Media Pro continues Mac support (Universal Binary even) and adds Vista compatibility. Features and fixes include updated Nikon libraries for compatibility with Nikon D80/D40 camera files, corrected issues with some .XMP sidecars not being recognized (Win), and fixed a problem where preferences might not be displayed correctly (Mac). You can read the version history (PDF) for more details.
I think Microsoft is doing a good job of moving the application forward for both Mac and Windows users. If you're looking for a solid Digital Asset Manager (DAM) for photos and other media, this application is definitely worth investigating. You can download a 21-day trial if you want to take a peek.