I live near the restaurant, and I'm amazed by the constant quality they manage to deliver all these years. Personally, I'm not a big fan of "Innereien" (innards) or "Blutwurst" (a special Austrian wurst made of pig blood, you could called it vegetarian's nightmare), but this is one of the few spot where you can eat anything without risk of disappointment. Big up for the beautiful pearl (schöne Perle).
Update: I published a German review on my blog: http://tinyurl.com/6me56t