Visted the stadium in Feb also (On the same trip as oafc-latics) It was stunning, it is up there with the best stadiums I have been to.
It looks even better packed with fans as seen in your photos - the passion for the football in Germany combined with the cheap prices must make for a great spectacle, especially when at the game.
Dortmund is on my list for stadiums to visit to, the 'kop' there looks absolutely stunning!