Configuring MOLAP writeback
Analysis Services introduced the capability to define a writeback partition with a MOLAP storage (the only choice until now was ROLAP).
You can check this whitepapers for a full list of enhancements: http://www.microsoft.com/sql/techinfo/whitepapers/sql_2008_bi.mspx
This new feature should help getting performance gains, as described by Microsoft:
"MOLAP Performance (FITS): New MOLAP-enabled write-back capabilities in SQL Server 2008 Analysis Services remove the need to query ROLAP partitions. This provides users with enhanced writeback scenarios from within analytical applications without sacrificing the traditional OLAP performance."