These are free of charge to licensed customers and include full documentation and PSS support.
The aim for the Excel Add-in for Analysis Services is to provide a fuller reporting solution for OLAP cubes than is natively enabled in Excel PivotTables. You can use it to build a report structure with different grouping and segmentation options, and you can then fill that structure with data from an OLAP cube.
Some nice features:
Drillthrough: the ability to see the constituent rows that make up an aggregation;
Suppress empty rows and columns (something not possible to do in an Excel PivotTable);
Elimination of selected dimension members from the report output;
Visual totals to only show aggregations of non-eliminated members;
Showing the unique name rather than the friendly name for all dimension members;
Showing server-defined formatting options (colour, font style, formatted value);
Ability to display MDX for the report as currently generated;
A free-from mode that allows a report to be generated using formulae rather than as a single monolithic block (like PivotTables are). This provides for a high level of customisation;
The ability to insert custom columns and rows in the middle of a report;
Leaf-level writeback for "what if" analysis.
If you're looking for a spreadsheet-based client into Analysis Services and you're finding PivotTables slightly too structured, this add-in is well worth evaluating.