This version of Custom Properties, beside fixing few bugs, takes advantage of J2.5 permission system. Frontend tagging can be enable to any user groups, including custom ones.
Other notable addition is the overhaul of tagging interface - both front and back end: fields are displayed using the OR-multiselect-with-picker-interface style. That saves a lot of space, especially when dealing with dozens or hundreds of fields values. The old mix of select and checkboxes is still available thou.
Native support for K2 images has been added too.
The full changelog is here