Main points to look for:
- Over- and Underexposure display has been improved and refined (Manual, p.132)
Detecting clipping point for overexposure zones display depending on camera's Make and Model (not available for all cameras)
Adjusting underexposure limit detection based on camera ISO setting
- Improved synchronization of XMP changes between ACR/Lr and FRV (see "XMP settings" in Manual, p.117)
- Touchscreen support (Manual, pp.68, 126)
- Option to verify data after file copy (Manual, p.36)
- The sorting and filtration of files in folders has been massively overhauled;
File sorting and filtering (Manual, pp.42, 165):
by Filename (naturally or alphanumerically)
by File type (extension)
by File modification time
by File size
by Shooting date (EXIF Timestamp)
by XMP rating
Save, Cancel and Restore filters (Manual, p.44)
- Folder tree editing (Manual, p.58)
Create subfolder
Rename folder
Delete folder
- Drag-drop into the folder tree (including Favorite folders) (Manual, pp.50, 112):
Copy or Move modes
- Drag-drop files into other applications (Manual, p.49)
- Selecting the position (below or above thumbnails) and detail of the EXIF data to be displayed in Grid mode (Manual, p.161)
Abridged exposure data (shutter speed and aperture)
More complete data (shutter speed, aperture, ISO, exposure correction)
Date & Time (from the EXIF data)
Camera name
https://www.fastrawviewer.com/blog/FastRawViewer-1-4-release-candidate