I have customized my own ReportViewerWebPart used in SharePoint 2010, to set the report URL dynamically, etc, and all is working fine.
Now, I am just trying to find out how I can override the actual behavior that grabs the report from the report library, and elevate the privileges of that execution account.
We have an issue with security and accessing reports with this webpart in a custom solution we are building, that this will help overcome.
A little background info, though not really needed: We are seeing that the Datasource connection, which using Integrated Security, is being impersonated just fine, but we have hit a threshold in the system regarding role to user mappings, which is causing
an error accessing a report when a user has over 1,500 role mappings. The same report works fine for a user that has less than the threshold, so it seems that the user's account is coming into play when accessing the report itself. So, because our farm service
account has very few mappings, that would be the idea account to use, and we will handle user-report security in a different way.