I would love to have the ability to filter activity by user!
Here's how I would use this feature: In my CRM, there are several companies that might be assigned to two different sales reps. Each rep would be trying to sell a different product to various contacts within the same company. I have workflows that add companies to our lead pool if no contact activity has been logged in the last 30 days. In this situation, I want to filter contact activity by the company owner so that both owners are accountable for logging contact activity.
For instance, Sales Rep 1 has owned a company for 60 days and last logged contact activity 10 days ago. Sales Rep 2 has owned the same company for 30 days but hasn't logged any contact activity at all. In this case, Sales Rep 2 would lose ownership of the company. Since Sales Rep 1 has logged activity within the last 10 days, they are not at risk of losing ownership.