I'm still pretty much a begginer, but i took a shoot at nl25/50 heads up.
I was very lucky , made 10$ into 90$ in ten minutes, but I realized that I wasnt playing very well, couse I sucked out on my oponents couple of times, so I stoped.
I think that HU is the most dificult game to play but I havent find any articles on this site about it, so any strategy oriented answer would be nice.