This is a great place for a good price in a hard market (Cambridge, super close to Harvard Square). I think the listing is pretty clear about what you're getting -- the building is an old building, and the apartment is an old apartment, although the host has painted/decorated etc. freshly so it has an updated feeling. The bedrooms are each a good size, and there is a nice living room and kitchen with eat-in table. The beds are pretty low-key -- essentially a pretty standard foam mattress on a basic frame -- but totally functional and the linens are comfortable. The location truly can't be beat -- so close to all things in the square, and there is a nice public park a block away and a pretty awesome coffee shop/cafe about a 3 minute walk away (Darwin's), not to mention all the stuff in the square. It is directly on Mt. Auburn which runs parallel to Memorial Drive at that point, so you do hear the Mem Drive traffic (e.g. at rush hour etc.) from the front bedroom, so if sound bothers you, you might prefer the back bedroom or another place, but you also get a lovely view of the Charles and nice light.
The only issue is with the parking situation. There is a parking space, but it is a tandem parking space with no room to "parallel" out of the space. That means that if someone is parking behind you, you have to locate them and ask them to move their car, or if you are parked behind someone, you might be asked to move your car. The host has a whiteboard in the foyer where parkers can leave their cell numbers so that they can contact one another, but obviously this is a pretty significant limitation on your freedom. For instance, I drove in from out of town, and planned to use my car occasionally while I was there, but also planned to do quite a bit of walking or using the T to get to dinners/activities. But leaving my car meant that I either had to be responsive to a phone call asking me to move my car if I parked behind someone, or else would have to hunt someone down if someone parked behind me (someone who could, after all, be anywhere public transportation goes in Boston!). Given that there isn't convenient parking on street, the lack of a true parking space really mattered. Fortunately this only became an issue late on Saturday and so I was able to park on the street near the apartment from Saturday pm to Sunday early am, when I was leaving town (that part of Cambridge doesn't have the 2 hour/permit restriction in place on Sundays, although it is in place on Saturdays until 6pm). Anyhow, if you are not planning to park a car it's not an issue, but the host should make clearer that the parking is a tandem spot with no way to exit if you are parked in, and that there is likewise a possibility that you might be asked to move your car if you park someone else in (which could be an issue if, like me, you had taken the T to Boston for the day).