My first visit was disappointing---see below for my description of the dirt meat. I stand by that account, but it is possible that the kitchen has ironed out the kinks, or that I was there on an off night.
It seems appropriate to mention that the owner of the business got in touch with me and he seemed genuinely concerned with ensuring the quality of their food. He offered to comp a return visit, which I declined, though I appreciated the gesture.
This time the meat was juicy as heck, and while it didn't reach the heights of the best I've had in Berlin, this was both an excellent sandwich (in its own right) and a real berlin doner. I'll be back to try the currywurst. Thoughtful selection of beer and presence of prime mate a plus.