While it's a beautiful film, you can probably live a while longer without having seen it. Daniel and Jana Pallaske are both excellent in it, but while it's the zenith of August's acting, it's not the be all and end all of Daniel's career (or German cinema). Self-destructing over another person is highly romanticized, which is a bit grating, though August portrays it magnificently.

Since you've enjoyed Der Baader Meinhof Komplex, I'll suggest a couple more dynamic German films starring Daniel: Good Bye Lenin! and The Edukators.