We enjoyed our stay at Xerxes' apartment. We didn't do much communicating with Xerxes, as we were pretty self-sufficient, but when we did, he was VERY quick to respond and great to work with. The apartment is a great space, very comfortable. It is also very well located. You're right by the start of the Freedom Trail and situated perfectly between multiple T stops depending on which line you need. There's a Whole Foods within walking distance as well as restaurants and bars (though we mostly ate in the south and north end).
A couple of drawbacks: There is VERY, VERY LOUD construction going on across the street that begins no latter than 7:00AM every week day. I understand that this is not Xerxes' fault, but as someone who was hoping to actually sleep in on my vacation, this put a major damper on things. I would recommend that you contact Xerxes before booking to see if the construction is still going on if you'll be there during the week. Also, the hot water supply is not great. 2 people really can't shower one right after the other and have a full hot shower, so just plan to space out the showers.