If you visit Berlin and don't go here at least once you're off your head. I've been 8 times in 4 (4 day) trips. And although that sounds obsessive, it probably is.
If all burgers were Steven Seagal movies, then the bird burgers would be Under Siege 1 & 2 combined.
Go here, get a burger, get fat and get tipsy. In fact, get drunk, the staff have great chat too.
Be careful when ordering napalm wings though. Despite them tasting great, I couldn't speak for about an hour after eating 2 of them. Immasculting to say the least!
As for value, I don't know how you can argue with 13/14€ for the meal you get. Forget the fact that its that money for a burger, it's not just a burger. It's the quality of everything on the (huge) plate that makes it good value.