Paul Graham's essays are always an excellent read, even when you don't agree with them.
For the record, while I think someone who has only written software for Windows using Microsoft tools has left themselves open to the worst kind of mind control, I completely disagree with his assertion that there are no good Windows hackers. And that you can't write decent software with Java? Balderdash. But I think he's absolutely right in this one.
What you'll wish you'd known is an essay aimed at high school students, wondering what to do with the rest of their lives. But it's not just good advice for students. This is a great tonic for everyone, encouraging and clear-eyed.
I'm not going to say any more. Just go read it.