My boyfriend and I stayed in the Modern Granny Flat for 4 nights, and had a great experience. The location is super close to downtown, but in a quiet neighborhood that removes you from all the madness of the scene. We arrived and the key was right where Kristine said it would be, the flat was clean and looked just as it does in the pictures, and had towels, soaps, lotions and other helpful amenities ready to go. As other reviewers mention, the shower is awesome! And even more importantly, the bed is very comfortable and there were plenty of pillows. We never used the a/c or tv while we were there, preferring the fan and sound of the birds chirping outside.
We walked to a coffee shop one morning and got a feel for the neighborhood, which is very cute and quiet, and appears to have a lot of neat looking houses going up all around. It was also convenient to have a driveway spot to park, as we had a rental car for the duration of our stay.
Overall I would highly recommend the Modern Granny Flat to anyone coming to Austin to visit, it was a fantastic place to stay!