I had a chance to visit the Daruma main shop. I got there around 5:45pm on a Friday (the shop opens at 5pm). There was already a line there when I arrived, but it wasn't very long, so I decided to wait.
After about a 20-25 minute wait, I got in. The waiting line is outside, slightly covered, but otherwise unprotected against any rain or snow.
The inside seated 12-14 total, at a very intimate squeeze. Ordering was simple, even though I spoke only very basic Japanese, and the menu has English translations on it. There are three cuts of lamb available, a normal cut, a more premium cut, and filet. The store also has a seating charge (170yen as of the writing of this review), which is provided as a small dish of picked vegetables.
I got the premium lamb, some rice, and a oolong-hai. Overall, the meat and food quality were fairly decent, and you grill the lamb yourself over charcoal. Total cost was just over 2,600 yen.
If you don't mind potentially waiting in the cold for upwards of an hour, and a cozy, but tiny dining space, I'd recommend this place to try.