Under the User's Profile > Activity there is already an activity and recently accessed records section. Neither of these are currently able to be exported but if the activity was amended to allow exporting, this could then be used for logs or for reporting such as user productivity.
Each piece of activity is already date-stamped, in chronological order and has a brief description of the action. Even if the report was split into three columns, the date/time-stamp it is from, the category of action (uploaded document, order taken, problem status change) and then the final column being an in depth description such as "User XYZ added document 'GenericDoc.msg' to Order 123456" - which is already the same style of message that appears on the activity at the moment.