Designing appropriate aggregations in SQL Server Analysis Services is a big issue that a BI developer must consider carefully. When I read Performance Optimization chapter of Professional SQL Server Analysis Services 2005 with MDX, I felt that I should study designing aggregation in more detail if I wanted to get a good performance on Enterprise Data Warehouse.
Although "Microsoft SQL Server 2005 Analysis Services Performance Guide" has been published in February 2007, I find it today! It describes some important tips in detail.
If you haven't read it, don't miss it.