I do not have 3D acceleration enabled, and I have no issue with the Fog of War. I see no difference.
Is just a small difference, the Fog of War without acceleration it looks like pixelated, with acceleration, is like a real "smog" transition between the black of the fog and the colours of the scenary, is a minimal small not really important detail. Also the spell effects use Aceleration If I remember well.
I am picky. Anyway i think I will play it without acceleration. :)
Yes, I see the difference now, but it's only a slight blur on the border. The actual fog is opaque black in both cases.
You can also see in my attached images why I don't use 3D acceleration. Look at the text and the details of the terrain in the 3D enabled image. All is blurred with OpenGL acceleration on my rig.
Attached images with and without 3D acceleration: