Arnold for Maya (or MtoA) provides a bridge to the Arnold renderer from within Maya's standard interface.
Features:
- Seamless integration with Maya shapes, cameras, lights and shaders.
- Image Based Lighting support, including a state of the art physical sky.
- Interactive rendering (IPR) allows parameter changes to be rapidly previewed without interrupting your work.
- Support for volume rendering with Maya Fluids.
- Support for Maya Hair and nHair.
- Particles and nParticles support, including particle instancer.
- Defer the creation of geometry at render time with the Stand-in placeholder nodes.
- Productivity boost: override sets, holdout mattes, shadow catcher, passes, UDIM style textures, and arbitrary primvar data.
- Extensible through plug-ins (Golaem, FumeFX for Maya, Yeti, Shave & Haircut).
- XGen integration.
- Texturable geometric lights.
- Deep EXR.
- Rendering of curves.

What's New:
Updates: official site does not provide any info about changes in this version.