Agree with Scottish Canuck. I also enjoy Dortmund because they're just fun to watch playing at their breakneck pace. Watching them do a number on teams like Madrid a couple of years ago was great.
They also have an underdog aspect to them after losing players like Sahin (immediately after he won top player in the league,) Kagawa, Barrios, Gotze, and Lewandowski who were all key contributors before being moved. They've relatively successfully been able to develop very good players, even when they've brought them in from somewhere else: Gundogan, Reus, Hummels etc...
I hope they keep it going