Mari is being used by LucasArts to make Starwars Level 1313.
They've ported their game shaders over to Mari so they have a 100% the same view in Mari that they have in-game. They can also export shader settings back from Mari to the engine. This makes it much more of a full look-development environment than just a texture painting tool.
All of the assets in 1313 are painted and look-developed inside of Mari.