Among the usual smaller improvements, fixes and additions, this update also improves Left 4 Dead 1 map support, making the map textures no longer flicker and the cables/wires draw properly now.
Here's before and after comparison:
There are some improvements to the Half-Life campaigns in Garry's Mod - The Half-Life 2 episodes now have their episodic behaviors enabled and disabled automatically which fixes progression-stopping issues such as antlion nests on Episode 1 maps not being able to be covered with cars. Breakable props on Half-Life 1 maps will now also properly drop Half-Life 1 items and weapons instead of dropping the Half-Life 2 items.
Hammer Editor got some updates as well, in addition to stability improvements you can now also use Middle Mouse Click to pan around the 2D and 3D views:
The dropdowns also display more data now, so its easier to find what you are looking for when there are a lot of options.
We have also updated the map compiling tools to allow more freedom to map makers - they will no longer remove models with 'wrong' versions during map compilation, which now also matches how Garry's Mod itself behaves.
Lastly a new Lua feature was added for addon makers - clientside entities, which allows to create completely customizable entities only on the client.
You can read the rest of the changes below.