Great point Brian! The ability to create a report template file that could provide the basic header graphics and page layout would be a huge boost to the reporting product.
I would also suggest that the "MasterReport" be a file that can be maintained separately from the "ContentReport" files. In other words, if I make an update to the MasterReport file (or ReportTemplate), those changes should be applied to all inheriting reports without having to resave/"recompile" the content reports (just like MasterPages and ContentPages, as Brian suggested).
Perhaps this is something could be implemented is manner similar to .NET MasterPages? The TemplateReport could have one (or more?) ReportContentHolder tags in which would act like ContentPlaceHolders, allowing report content to be added in the actual report files.
Telerik- Are you planning any feature similar to this for the upcoming September beta? If not, you really should! :)