It's propaganda, not much different from a Dick Cheney speech in that regard, except bin Laden invokes God a lot more and doesn't snarl as much.
The text of bin Laden's message is something you should read. Here's an especially intriguing comment:
We are people who do not stand for injustice and we will seek revenge all our lives. The nights and days will not pass without us taking vengeance like on Sept. 11, God permitting. Your minds will be troubled and your lives embittered. As for us, we have nothing to lose. A swimmer in the ocean does not fear the rain.