For anyone looking for more information on the Viewport 2.0 API that was introducted in Maya 2012, I posted a White Paper here, (this page is also a great resource for API items):
but a direct link to the whitepaper is here, which is a collaboration from the rendering team, authored by Matthew Lausch, Autodesk:
http://images.autodesk.com/adsk/files/viewport_2_0_api_gold.pdf (updated pdf)
Here is the Introduction for users doing Google searches:
Maya 2012 introduces a new set of API classes for defining custom drawing, shading and effects in both Viewport 2.0 and Hardware Renderer 2.0 (the new batch rendering version of Viewport 2.0).
Maya’s Viewport 2.0 represents a brand-new rendering architecture in Maya that has been written from the ground up to deliver high-performance on large scenes on top of a programmable shader system offering high-quality per-pixel lighting and effects. This, unfortunately, makes it incompatible with many of the existing Maya API classes, due to their dependence on system memory geometry data, C++ driven rendering, and high state switching overheads. As a result, most existing plugins will need to be updated to support the new API classes in order to work correctly in Viewport 2.0.
This document introduces the new classes and highlights the migration paths from the old API to the new one. In most cases, it should be possible to write plugin nodes that simultaneously implement both the new and old APIs where required, thus maintaining a single plugin that will work in both viewports while artists, tools and pipelines are migrated to Viewport 2.0.