[quote=Phobos]
Wait, how many people have observation Haki?.__. Cause my Devil Fruit just became useless if it's more than Deuce ;-;
[/quote]

I thought Deuce was the only one honestly until people came out and started saying they did xD

But Kenbunshoku is to sense the presence of others and slightly predict moves, so it depends on how you use the Devil Fruit really.