In my opinion, Power Pivot is the most agile and cost-effective BI / Reporting solution. It has very low (or zero) start-up costs, powerful back-end engine which can easily handle millions of rows, nice and intuitive OLAP-model interface, and Excel front-end. It can be connected to number of different data sources (not limited by MS products). The results can be delivered via Pivot tables, Charts, or cells with Cube functions.
It is a perfect solution for financial reporting: any ad hoc reports as well as standard ones can be created with dynamic connection to your core ERP and others Financial, Budget or HR systems.