Andrew,
Is anyone else using PM successfully with Capture One? These two applications have been around for awhile and are both incredibly popular, so I find it hard to believe that they don't work together.
Anybody have any advice about using PM with C1? Although, I just read that PM's ranking system isn't compatible with Bridge or iView, so considering all these incompatibilities I don't think I would buy it anyway. It obviously has a lot of strong points, and a lot of fans, but if these apps can't talk to each other and transfer vital data like IPTC info, Labels and Ratings, then I don't see how they can be incorporated into a solid workflow.
If C1 is incompatible with embedded IPTC and/or XMP data in RAW files then just configure Photo Mechanic to use XMP sidecar files. If C1 is not compatible with XMP sidecar files then PhaseOne needs to fix their software. It sounds like C1 has some naive parsing code in their software. They are likely expecting certain values to be located at explicit offsets and are not parsing the files properly, thus making them incompatible with RAW files with embedded metadata.
Our Color Class system is not a 5-star rating system. Bridge has a label system but it allows every image to have its own label name and requires the user to be consistent. iView Media Pro does have a color label system, but it repurposes the IPTC Urgency field which we don't really approve of. Photo Mechanic version 4.5 (in development) has an additional 5-star rating system that is fully compatible with Bridge and any other software in the world that uses XMP metadata.
Whether or not C1 will work with 5-star ratings found in XMP data is unknown to me since I do not own a copy of their software. I hope that they will support XMP since it is rapidly becoming an industry standard way of maintaining metadata for images and other types of files.
If you want to try using XMP sidecar files and want to test their usability in C1, then let me know. I'd be happy to help you get things configured properly.
-Kirk