With SQL Server 2008 just released. I was keen to see how the new standalone Report Designer (Report Builder 2.0) turned out. Well, I found out it's not released with the RTM! It will be available for download sometime later. To find out more about the release plan of Report Builder 2.0 have a look here.
At first glance, it appears that the RC0 version of Report Builder 2.0 still works with SQL Server 2008 RTM. Search for ReportBuilder.msi and you might find an old copy of RC0 floating around.