Pros: REAL Color Management (i.e. using custom monitor profile), even for RAW/DNG files! There aren't many applications around that will do this.
Shows a lot of EXIF data, much of which is not available through other viewers, but require a specialized EXIF program. Also, items to be displayed can be user-selected. Very nice!
Cons: Still Beta, so a few quirks are present, but no big deal.
Shortcut keys use numeric keypad, which is not convenient for me. Unfortunately, many shortcuts cannot be customized.
Other Thoughts: This Beta is MUCH faster than the previous version I tried, and is now definitely useable for viewing color managed images.
I'd LOVE to have a left mouse click zoom and pan, as in Faststone and FastPictureViewer, since once you develop a taste for this feature you don't want to do without. Also, more control over shortcut key assignment. And finally, a side-by-side compare feature (a la Faststone) would make this "perfect".
For me, the above features would make this application unbeatable as a viewer.