When working with Sql server 2008 reporting services I found a new control named Tablix. [Of course there are plenty of new features] This is a mix of both Table and a Matrix. The main and great advantage of it is when we drag a table or matrix to the report body you can't find table or matrix any more. The report control automatically convert it to Tablix. Now, it's very easy to show the complex and grouping of data with this control.
The interest thing in 2008 reporting services is, When I open report builder 2008, BIDS 2008 I didn't find the Tablix control at all and started researching for the control. Stupidly searched in google like download tablix control ssrs 2008 etc… But, once I drap and drop the table or matrix and right clicked for properties found "tablix properties" in list of properties there. Then understood the whole concept and implemented the reports very fast.
Hope this post will help you understand it. Let me know what you think.