There are no major issues apparent from an inspection of the plugin.
Reason for the 'Use with caution' result
The plugin has been given this recommendation at the tester's discretion:
This plugin logs user activity including user names and IP addresses. There is no option to not log IP addresses. Therefore, the user of the plugin should be aware of and handle any potential data protection concerns. This may also be a consideration if exporting the activity log to CSV and disseminating it further.