I\'m about to start using the MS ReportViewer in a WPF application by placing the ReportViewer in a WindowsFormsHost.
Is this the correct approach? What is the best
We've definitely had success just using the WindowsFormsHost. I haven't been involved in creating the RDLC files themselves, but I believe they were designed (as you say) in a WinForms project and then copied across.
Note that if you don't need local reports you can use a WPF Frame control and point it at the URL of the server-based report (it renders it like a web browser would). This works really well for us too.