They're neat dogs - I knew a few with horrible, uncontrollable aggression towards dogs, but they were both from a BYB in my hometown - so I think it was an isolated pair of cases.
One of my trainers had a Standard Schanuzer named Misty... she was the best behaved dog I have ever seen. Her owner would put her on a downstay on a pallet of dog food at Petco, walk away to the other end of the store, and Misty would stay put - no mtter what! If you tried to pull her off, she's struggle to stay where she was left!
He never ended up finishing her, she only needed a major but her heat cycles started to act funny - she'd come into season several times (6+) a year, so he had her spayed.