My parents and I stayed in Guy's place for two weeks, and we loved it! We were out sightseeing most of the time, but enjoyed all the time we spent "at home" too. We were a little surprised at first because it is a basement apartment, but there are big windows that let in lots of sunlight and it is on a quiet street, so not at all noisy. Plus, it was kind of cozy! It had a great heating system (we went in winter) and the temperature was always comfortable. The beds were both very comfortable, and the couch-bed was easy to use and figure out. The apartment is decorated nicely and tastefully, and was very clean. It is also in a very central location, only a 5 minute walk to the nearest T station and to Boston Common and lots of shopping. The washer and dryer are right there in the building and a bit expensive, but very convenient.
Guy was out of the country when we stayed there, but was very helpful and friendly through e-mail. A friend of his let us in and showed us around, and was available in case of any problems.