All being well, Azure will be even faster in using the GPU & driver via OpenGL that Cairo was in using the GPU & driver via Xrender.
The back-ends for the Azure library are Direct2D, Quartz, OpenGL, Direct3D, and Cairo. On Windows, Direct2D is the primary target for Azure while Apple Mac OS X users will have Quartz, and Linux users have OpenGL. If hardware acceleration fails, Azure can fall-back to having Cairo sit underneath. Cairo is also used for Gecko's printing support. Mozilla's copy of Cairo has also been modified to take advantage of Azure's internal stateless surface API. Direct3D 9 and Direct3D 10 back-ends for Azure are also being developed.