I recently wrote a whitepaper highlighting a great tool by one of our partners: SoftArtisans OfficeWriter.
OfficeWriter is a design tool and custom rendering extension that lets you use Excel and Word documents as report layout templates. This differs from conventional out-of-the-box renderers that translate RDL-defined layout into HTML/PDF/CSV/etc.
It's a different way of thinking about report design, definition, and rendering. It has certain limitations, but what you gain is an Office-based design experience and high-fidelity Excel and Word output from Reporting Services.
If you have a specific need for rich Excel or Word export, I encourage you to read this article and contact SoftArtisans to get set up with an eval: