I recently discovered that we can only download 90 days of activity history tracking at a time. This is a severe limitation! It looks like the activity is tracked for the life of the sheet, so I'm not sure why we can't download a year's worth at a time (or even the whole sheet activity).
Obviously, it may take time to compile that data, but we already have to send a request to Smartsheet to compile the 90 days data (it doesn't download right away), so I would think that would be doable.
Separately, there appears to be no way to filter the sheet by actions taken by a "Publish User". We often have sheets which we publish with links to edit by anyone. People who view/edit these sheets don't have an email address associated with them. Unfortunately, I guess only collaborators with emails are supported to filter Activity Logs right now, which isn't very useful for us.
It would be great to add these two features to improve Activity Log tracking.