Journal of Accountancy has a great look at PowerPivot in the September 2011 article Pivotal Advance Boosts Excel’s Power.
I’m seeing more and more accountants embracing PowerPivot as a natural extension of their Excel skill.
Pivotal Advance Boosts Excel’s Power
Archived post from 2011. Dynamics GP and the links it points to have changed since; check current documentation before relying on version-specific steps.