A lot of compatibility and improvements, many bug fixes, and several new features were added, including support for DeePBSP and uncompressed ZDBSP nodes and dynamic music changing through the new MUSINFO lump. On the GLBoom+ front, there is support for GZDoom skyboxes, custom detail texture definitions, and blending of animated flats and wall textures.
Various fixes and enhancements were made to OpenGL rendering, the automap, graphics glitches, key binding, and other things. Notably, it lets you disable specific OpenGL features instead of disabling the whole of OpenGL. Also, it allows you to keep track of the damage caused to specific things as you play.