Son Of Sun, Brother Of Light, Kingdom Of Darkness.

Just out of curiousity before i make my final decision on the matter, Is there any real down side to killing Gwyndolin?
I stood at his white light for half an hour, Um-ing and Ah-ing on whether i should or not, But thought i should ask, To be safe. The strategy guide isn't much help on the matter.
Does anything drastic happen to Anor Londo, That i may regret terribly should i rip his head off?

Gilling Gwyndolin will simply prevent you joining he darkmoons, and let you be invaded by DMs constantly as you'll get a ton of sin which (apparently, not 100% sure on this) can be removed thorugh absolution.

So nothing happens to Anor Londo? I can continue to farm creatures there without a problem? Will The lady of the darkling attack? Ariamis will remain open to me?

Ariamis will remain open. The firekeeper will attack you, EVEN if you absolve your sins (I thave done this). You can continue to farm the enemies with no problems.

Beautiful! Cheers Dough =)

No problem

Kill the firekeeper wench anyway for her soul!

One big thing is that if you ever die in dark Londo, you respawn at the first anor londo bonfire unlit, meaning you either need to run across the bridge to get back to the chamber of the princess, or back track into Sen's.

Yes but he's not turning it dark, just killing dolin.

Don't all the Silver Knights dissappear though?

1) even if he turns it dark some wil stay. And 2) Killing Dolin has no effect on the world apart from getting you sin.