A great post by Barry O Sullivan on what, in my mind, is one of the biggest advantages of event sourcing: the ability to create projections.

Projections are a necessary part of any event sourced or CQRS system. These systems don't rely on a single generic data source such as a normalised MySQL database. Instead you build up your data sets by playing through the events, i.e the “film”, "projecting" them into the shape you want. This allows lot of flexibility as you're no longer bound by a single data model on which you have to run increasingly monstrous SQL queries (12+ joins anyone?). With projections you can build a data model specifically for the problem/question at hand.