This series of tutorials are meant as an introduction for first time users to Arnold for Maya. The original scene files used here are setup for the mental ray renderer. Mental ray is a biased renderer which uses caching algorithms that introduce artifacts like photon mapping and final gather. Whereas Arnold is a highly optimized, unbiased, physically-based 'Monte Carlo' ray / path tracing engine. Therefore, you should find it quicker and easier to achieve photo-realistic results with Arnold due to its simplified workflow and physically accurate nature.
You will find that much of the same shading terminology carries over from mental ray to Arnold for Maya as both renderers are 'technically' ray tracers. The scene files used in these tutorials contain mental ray's mia shader and Maya's Blinn shader which will need converting to Arnold's more physically accurate shaders. In particular, we will be using Arnold's multi-purpose Standard shader to create various materials.
The original Maya scene files for this series of tutorials can be downloaded from Autodesk's Hyperspace Madness production.