The SQL Server 2005 SP1 CTP is now available. This update fixes a number of Report Builder issues in the original 2005 release, including one that is fairly critical.
The most critical issue is related to report processing and database collation. Model-based queries were incorrectly returning some entity key grouping values that differed only by case. Because case-insensitive report processing (the default) would combine any such rows, some reports would not actually display all the rows returned by the query. For a variety of reasons, many reports were unaffected by this issue, but some reports that display data from a large table with an auto-increment primary key could fail to display a significant number of rows returned by the query.
Even with SP1, if you are creating any report in Visual Studio Report Designer, you can get yourself into this situation by specifying an incorrect value for the dataset's CaseSensitivity property. If the value you specify does not result in a match between the behavior of report processing and the underlying database, you can expect subtle inconsistencies in your data.