I've experienced two problems so far:
1) Scan to catalog choked on old images from Canon Powershot SX20 IS. I could add the other 36,000 or so images that I wanted to test without problems, but every time I tried to add one of these files, the catalog hung while attempting to update the metadata. I cannot see any problem with the metadata. I tried deleting the catalog and adding a single file (obviously one of the Powershot files), and had the same problem. I removed the metadata using ImageOptim, and then was able to build the complete catalog.
2) I am completely unable to add a collection to my catalog. I've right clicked everywhere on both the navigator and organizer views without any dialogue box appearing. I've done this with and without active selections using both browse and filter. I assume that I must be doing something wrong, but I don't know what it is. I'm using PM6+ build 3029 on an iMac 27" retina display with OS Mojave.
Otherwise, the app seems impressive. Great speed in searches. I'm not a PM maven, but the UI seems pretty straightforward, albeit somewhat clumsy with dropdown menus that are too long. I would also hope that the final version will allow us to customize settings so that preferred search criteria are easier to find.
Looking forward to the next beta version.