Great story. It isn't the same as the other Dark Harry stories- quite refreshing to say the least.
You are also not portraying Harry as supremely brilliant, but someone who could get his ass kicked if he was battling someone genuinely good.
I don't think that this is on ff.net. Posting the story there might add to the number of people reading this story. Not a ff representative or anything- just a tip to spread it to more people.
Your battle scenes are quite good too.
Well done, and hope to see regular updates.