In researching the list of improvements for SSRS 2008 R2, I found the following list which is quite impressive!
http://msdn.microsoft.com/en-us/library/ms170438.aspx
The following Reporting Services features are new in SQL Server 2008 R2 (see original link for details)
- SharePoint Integration
- Collaboration and Reuse
- Data Sources
- Data Visualization
- Report Layout and Processing
- Aggregates, Expressions, and Functions
- Report Authoring Tools
- Cache Refresh Plans
- Report Manager Enhancements
- Business Intelligence Development Studio
- New Web Service Endpoint
- New Report Definition Language Schema