To me, it doesn't matter. I admit that men with long or otherwise attractive hair (healthy, glossy, well-tended but not overmuch) does attract my glance, but it is not a feature that will attract or repell me with regard to a man.
I tend to be a bit wary with men who pay too much attention to their hair... as well as any other aspect of their overall appearance. That is a signal that may mean, in a combination with other factors (never on its own) that the man may be either too fond of other people's attention to care for somebody truly, or that the man may be too much in love with himself to love somebody else really. The two are slightly different, but in both cases my chances of becoming the most important person for that man are not very great.
Which does not mean I will not give them a chance to prove me wrong :)