This feature can be used to develop ASP.NET or WinForms solutions that sport SQL Server Reporting Services style reports, without having to deploy those reports to a Reporting Server. Reports are deployed as RDLC files with your solutions. In fact one doesn’t even need SQL Server, since these reports can be programatically bound to objects such as DataSets, a huge plus for ditributed n-tier designs where the UI layer does not have direct access to the data store. This also means that one can use any imaginable back-end data store including XML and CSV files as long as data can be loaded into binable objects.

The report viewer control is similar to Reporting Services report viewer, with nifty features such as paging, searching, and export (PDF, Excel, CSV) features. My only complain with the ASP.NET version of the report viewer is that it does not directly support printing. Reports have to be exported to PDF in order for one to print. This was a gotcha with the first versions of Reporting Services report viewer as well, but later they added printing support to the control (perhaps through ActiveX) in Reporting Services SP1.

You can find more information about this feature at GotReportViewer.