I have been using the preview for several months.
Good:
- Response is snappier for all activities, especially drag/drop
- Menus more consistent across all components
- Export to .png, .jpg, .pdf reliable and better quality
- Color (skin) behind menus makes them easier to identify
- Modules SMALLER.
Bad (Preview bugs?)
- Outlook required rebuilding identity a few times. No data loss.
- Auto-recovery failed until reboot. No data loss.
2016 is an excellent update.