This is a superb and intelligent film which gives you a look at your future.
The commentary is almost as interesting as the movie. One interesting nugget is the following contradiction: the filmmakers say repeatedly that only 3% of Muslims are terrorists (a claim which is highly dubious). Then, later they quote their English Muslim sources as saying that "their communities are full of people like this" (the terrorists portrayed in the film). If there are only 3%, how can their community be full of them?
The film also shows how easy it is to smuggle radioactive material from the Middle East into England--not "possible." Easy!
Another irony is that the filmmakers gush about how wonderful "multiculturalism" is, blissfully unaware that their own film demonstrates one of the consequences of multiculturalism.
Generally, they don't reveal any tactical information that isn't easily available on the Internet, but in one discussion of how the terrorists communicate with each other, they do. What they don't realize is that such methods show that the terrorists know exactly which methods of communication are being monitored by the government. How do they know such things without inside information?
Finally, at some point, Western governments are going to have to make some tough choices. For instance, even if only 3% of Muslims are terrorists, it is still true that if you deport 100% of your Muslims, you get rid of the 3% who are terrorists. But even though all the other methods have failed miserably to get rid of the terrorists, such an option is regarded as unthinkable.
But consider: Which is worse, (a) to have 300,000 people killed by a dirty bomb and incur billions of dollars of damage or (b) to deport all your Muslims?
It's this tough question that Western governments are going to have to ask eventually or else go down to defeat, because the counter-terrorist experts all agree a dirty bomb will eventually get through.
Note: the HBO DVD puts five minutes of advertisements at the beginning of the film which you can't skip over, can't fast-forward over and can't get out of buy pressing the MENU keys. Start the DVD five minutes before you intend to sit down to watch it.