Blender 2.63 Release Notes
Over 100 of crucial bugs were reported and fixed after 2.63; this has been released now as 2.63a.
BMesh is the new Blender mesh system with full support for N-sided polygons instead of only triangles and quads.
In particular there is a new Dissolve tool to remove vertices, edges and faces without making holes in the mesh, a new Inset tool to inset faces, and a much improved Knife tool which takes advantage of N-gons to generate clear cuts. Tools such as subdivide and loop cut will also generate clean topology because faces no longer have to be triangulated.
Among the features added in this release are support for a panoramic camera, mirror ball environment textures, render layer mask layers, a shadow render pass, ambient occlusion, float precision textures, and viewport display of background images and render layers.
Motion tracking got a few smaller improvements, mostly related to 2D stabilization and a few smaller tools.
Portions of the mesh can now be hidden in sculpt mode to improve performance and access parts of the mesh that would otherwise be difficult to access.
Other new features in this release include Movie Clip option for the Sequencer, a compositing node to output multiple files at once or multilayer EXR files, new tools for linking and detaching nodes, more particle rotation options, theme support for cameras and empties, and Linux support for drag n' drop from external applications.
This release was mainly focused on stabilizing BMesh, but also includes 150 fixes for bugs that existed in previous releases.