Without spoiling it too much for those who may want to read it one day. What exactly made it so crazy? I'm kind of curious.
OSC re-wrote Tony's origin so that he was a weird-ass freaky experiment-gone wrong with brain tissue through his whole body, so he was literaly a walking brain and he was in constant pain and had to be coated in this weird blue 'armour' paint to avoid feeling pain and he could regrow his limbs like *#&$ing Wolverine.
it totally contradicted the origin Brian Bendis wrote for Ultimate Stark in Ultimate Marvel Team-Up and didn't really add anything to the character.