This new version takes into account the smooth lights. By default (and for standard lighting compatibility), the opacity of the slopes is set on 0, but this parameter can be modified in the property file that you can find in the .minecraft/ directory (after launching the game once).
To install this mod, you will need Modloader 1.7.3
Here are the traditional readme file and property file
Here is what you should get with the smooth lights:
Here is what you should get with the smooth lights:
And there with the standard lights (former versions):
