It works, but it makes the game so slow, so I removed it.
iBlurDeferredShadowMask=5fInteriorShadowDistance=3000.0000fShadowDistance=4000.0000
These 3 shouldnt really affect performance, they might actually improve it somewhat. But these...
iShadowMapResolutionSecondary=2048iShadowMapResolutionPrimary=4096
Can drop your FPS like a rock

. The last one is the biggest frames killer, but can also have the biggest effect on shadows.
For me I cant use iBlur because it makes any object up against shadows basically glow

, I think its an ATI issue.
Edit: Dropping shadow distance isnt all that bad really, most of the time youre wandering through a forest and cant see passed the tree in front of you. But youll notice it in towns.