I've been told by a few women that they enjoy greasy hair on guys. They say they can't put their finger on it, but they like it.
I found this out mainly through girls I was dating. They'd want to meet up, so I'd tell them I'd have to take a shower first (I have long hair and I wash it pretty much daily, and it grosses me out if it's left unkempt for too long). They'd then reveal that I shouldn't, because they like greasy hair.
I do notice that when I'm on the subway or walking down the street that more women look at me than if I had my hair nicely washed and kept. Maybe it's an "EWWW DISGUSTING!" kind of look, but either way I get a lot more attention.
I have a theory that may or may not be bull, but is it possible that maybe pheromones are more present when a person is unwashed? Or maybe the smell of BO just turns women on? When I go out unwashed I'm not talking about being a sweaty, smelly, disgusting mess, I'm talking about taking a day off showering so I'm not at my cleanest.