Blender v2.58a (ENG/2011) + UA-IX

Additions
More flexible size options for particle billboards. This adds scale factors for width and height of billboards, relative to the particle size. It's useful when the particle size is primarily used for collision and the like, so the billboard appearance can be adjusted independently. Also allows non-square billboards.
In addition the billboards can be scaled by the particle velocity with optional head and tail factors (similar to line drawing options). This allows for pseudo-motionblur effects. - r37760
Addon UI: button for removing addons which are installed to user/home paths - r37950

Python API:
Python application event handlers - r37795
adds bpy.app.handlers which contains lists, each for an event type:
render_pre, render_post, load_pre, load_post, save_pre, save_post
each list item needs to be a callable object which takes 1 argument (the ID).
callbacks are cleared on file load.
mathutils.geometry.intersect_line_sphere(l1, l2, sphere, radius, clip=True) - r37820
RenderEngine API: add self.report() error reporting function for render engines, works the same as for operators. - r37916

Fixes
Essential Fixes:
fix: Tile-able displacement map / tile-able painting regression in 2.58 - [#27782], r37899
fix: bake crash with deep shadow, strand and children - [#27807], r37970
fix: incorrect use of GL_ARB_vertex_buffer_object, could crash blender - r37881
Thumbnail save for .blend crashed, when being in editmode for a mesh that has other object users as well. - [#27765], r37810
fix: Multires lost from 2.49 file in 2.5x - [#27710,], r37837

Other Fixes:
CMake was installing .bfont.ttf in the config dir which made updating from the previous blender version fail - r37725
fix: Driven properties not checked for legal UI bounds - [#27726], r37744
GHOST Cocoa: move y origin top/bottom conversions out of windowmanager module and into GHOST. Also fixes a problem where e.g. the user preferences window would not open under the mouse cursor correctly. - r37765
revert commit 27133: Committing patch [#27133] "Fix for for Object Color in BGE" by Kupoman. This was causing a lot of backward compatibility problems and side effects. - r37773
W special menu for changing orthographic camera lens scale was missing - r37782
fix: Black and White Render doesn't work and/or Saves as a Blank screen, convert to grayscale when saving renders rather then only writing the red channel. - [#27746], r37783
fix: Modal operator in Special Menu (W) ignores continues grab - [#27747], r37784
fix: Smart UV project no longer works in 2.58 failed with active, unselected objects. - [#27742], r37785
free_bvhtree_from_mesh was incorrectly using sizeof() when clearing memory. - r37787
Fix undeterministic behavior of volumetric renderer - [#27748], r37802
Made clearer in the UI that the approximate multiple scattering always enables light cache
Fixed a potential problem in anisotropic scattering
Default startup theme used same node header color for "in/out" nodes as for "inactive or undefined" nodes. This made it impossible to see which of the output nodes in node setup was 'active' - [#27761], r37808
fix python errors when the sculpt brush is None - r37836
fix for a leak in sound_read_sound_buffer(), used when drawing the sequencer waveform. - r37845
fix: Set Bone Flags - No Scale - Toggle fails - [#27778], r37850
fix: On clicking in a non-active Blender window (when you activated others), the mouse position of the first click was still the old position. - [#27768], r37854
fix: Blender player on OSX not working - [#26850], r37861, r37862, r37865
fix: Smart UV Unwrap Results in Overlaps - [#27787], r37889
Closed regions didn't always draw the (+) icon right place, confusing for users. - r37986
fix: foreach_get was failing on readonly properties - [#27820], r38006
fix: Outliner does not update when parents are cleared - [#27816], r37999