User blog comment:Dmurray1031/Luffy's newfound speed./@comment-3079795-20110506234513

It's a combination of the fact that Luffy is an experienced fighter and he could predict the Pacifistas move with his haki. That's all there is to it. As for the lightspeed discussion going on here. ..

Admittedly, yes. Kizaru can move at the speed of light, as much as he wants. But take in the fact that even though yes, this is One Piece, at the most basic level the characters are human. Regardless of how monstrously strong a character may be they are human (well, ignoring Fishmen & any other exceptions). Because of that, it stands to show that even if he can move at the speed of light that doesn't mean he can process what he's doing. Zooming up to an enemy is one thing, but constantly moving at the speed of light is beyond human comprehension.

So yes. In theory Kizaru could be an unstoppable god who moves at the speed of light and could kill you before you knew it. But in practice he would be unable to control his movements and would rush around blindly like Kuro (o.k. that technique is deadly so bad example, but you get my point)