Kathe & Lisa's place is exactly as advertised and absolutely perfect for a short break in Boston (we were there for 5 days). It is extremely clean, the bathroom/shower is great and it has all of the amenities that you would need. They even left us some yogurts and OJ in the fridge as well as throw away toothbrushes in the bathroom!
The self-check in and check out is extremely easy (you get sent a code for the front door) which takes all of the stress away when running to our from Logan like we were! While we only briefly met Lisa and Kathe in the hallway, their communication was excellent, answering any questions we had within a couple of hours. They even gave us a recommendation for where to eat in the North End given the volume of Italian restaurants in that part of town! They allowed us to leave our bags in a different room for the day when we checked out as our flight was not until 7:30pm that evening which was also much appreciated.
The location is very good - The South End is lovely (classic Boston red-brick neighborhood) and the apartment is literally a 1 minute walk to Tremont Street which has a catalog of excellent restaurants. It took us about 10 minutes to walk to Back Bay T station, the heart of Back Bay (Boylston St/Newbury St/Commenwealth Ave.) and Boston Common so it is well located for all of the major tourist sites.
I will be recommending Kathe and Lisa's place to anyone I know travelling to Boston and hope to return one day myself! Thanks guys!