CROSS JOIN with later PIVOT going rather slowly
I didn't find any way to speed up the PIVOT operation - it's just a big operation that takes time with a lot of data.  The one thing I did that seemed to speed things up a small amount (perhaps the addition concatenation operator implemented more efficiently in SQL Server) was to change CONCAT('Downloads_', usr.[OrganizationName]) to 'Downloads_' + usr.[OrganizationName].  The rest seems to be pretty much optimal.