This is a really interesting article I would encourage everyone to read before diving into this discussion. It is an interview with a psychologist at a Danish prison who dealt with the therapy and psychological needs of a large criminal Muslim immigrant population.
Among Criminal Muslims | FrontPage Magazine
It is too long to include in-line, but the basis of his findings were that people raised in a Muslim culture have different ideas about anger, self confidence, honor, individual responsibility, and because of these, it his his opinion that integration isn't just unlikely or impossible, it isn't even desirable to either party.
Be forewarned, some of the ideas he presents in this article are very "non-politically-correct" and potentially offensive, but I think it's important to read, regardless of how much weight you give his opinions.
He certainly presents a framework that supports a lot of the (to our Western minds) completely illogical/irrational actions Muslim society has taken, in terms of honor killings and the response to the Draw Muhammad day.
Does anyone who has interacted with Muslim societies have any supporting or contrasting reports/evidence/opinions to his?