I had a chance to try John Mueller's in Austin on Saturday. I had 1/2 lb of brisket and 1/2 lb of sausage.
The brisket was quite good, with nice charring on the outside and noticeable smoke flavor. Plus, I received two end pieces as samples. The sausage was good, but a little lean and mealy to my taste. My 3 yr. old agreed as she favored the brisket (but she usually is a sausage hound).
The pork ribs that were a special looked good, but I could not manage them.
I also had a side of pinto beans and a side of green bean casserole. The pinto were Ranch style beans with an enormous amount of cumin and a little cayenne added. Not very good. The green bean casserole was very heavy with a cream sauce. Also not very good. Skip the sides.
Atmosphere was very good; the place looks and feels like a barbecue joint.
All told, very good brisket. Probably best to take it to go and get better sides elsewhere. And, I would like to check out the pork.