Not a Dortmundfan but I never heard any complains on that front.
He is an incredible player, 24 till next! october and I would take him for my Bayern any second. And that is saying something, taking our talent pool into account.
I get the feeling that he knows what Dortmund did for him and that he has to pay something back BUT he just came there age 22. He has yet to prove himself after his long injury but in terms of talent he is a guy who can play everywhere.
And IF he has 1 or 2 great seasons there till 2015/16 he could be tempted to try something new.
Reached a CL final with Dortmund, scored there. Could be enough for him with this club. We will see. But only United or Chelsea in England for me. City has a bad name in Germany atm.