Dark Souls - 30FPS vs 60FPS
Looks like running at 60FPS using DSfix can have some weird effects. I'm almost certain running at 60FPS made the Iaito Gap jump impossible. The first two attempts were made at 60FPS; you can see I wasn't even close to making it. After logging out and limiting the game to 30FPS I made the jump with lots of room to spare.
I usually make this jump on the first try but failed 10+ times in a row running at 60FPS. The instant I swapped to 30FPS I made the jump just fine.
Update: I have heard from other people on the Internet that this is definitely a thing. I've also confirmed you cannot roll to the roof with the Asylum Key in Firelink Shrine while running at 60FPS.