The ExecutionLog table in the SSRS database (named ReportServer by default) contains quite a lot of nice information about the various reports in an SSRS environment.
For example, you can find out how often each report is used by whom, which formats and statistics on execution times for each dataset and rendering of the report. As an example, execute the query below to find out who last looked at each report and when it was.
WITH ReportExecution AS ( SELECT ReportID ,TimeStart ,UserName ,ROW_NUMBER() OVER ( PARTITION BY ReportID ORDER BY TimeStart DESC ) AS rNum FROM dbo.[ExecutionLog] t1 JOIN dbo.[Catalog] t2 ON t1.ReportID = t2.ItemID ) SELECT c.NAME AS [Report] ,re.TimeStart AS [Last executed] ,re.UserName AS [User] ,c.[Path] AS [Path] FROM ReportExecution re JOIN dbo.[Catalog] c ON re.ReportID = c.ItemID WHERE re.rNum = 1 ORDER BY re.TimeStart;