I'm not too worried about the graphical options since we can usually use a 3rd party program like nvidia inspector to get things like msaa, AF, etc.
Speaking of, are there any profiles on there that use the same engine as dark souls? I'm away from my computer now and can't look.
Race Driver GRID and the DIRT series all run on Phyre Engine and they look very nice on PC.
What I am worried about is going through gfwl means patching the game is going to be a joke. From has to pay Microsoft a huge upfront cost just to put the patch through, then it takes a month or so to get it approved.
Dark Souls hasn't gotten patched since November, so I wouldn't exactly expect frequent, expensive patches to be a huge problem. Also, I don't think they necessarily have the same cert process on PC.