Instead of totally bashing the place, I'm instead going to offer suggestions for whoever might book this next:
1. location: take the meaning of downtown literally. If you're not familiar with San Diego, like we weren't, it's going to be very big city like. You will be surrounded by big buildings and semi-busy streets. It's not some quaint small downtown, you will need to walk a bit to get to that. When we were there, there was also a lot of construction noise going on, which didn't help.
2. parking: this might be an issue with downtown San Diego as a whole, but finding parking can be an issue. Park it by Market is ideal, but when its $25 overnight each weekend-night, it adds up fast over a whole weekend. I would suggest taking the train, but the station is a bit far from this place. I think it could be done with public transportation, though.
3. Gaslamp district: if you are in San Diego to barhop and explore just downtown, then this place is for you. It's great to walk to restaurants, but we basically had to drive to get to most other places, maybe except for the Sea Port district (USS Midway). It's "conveniently located" if you're okay taking the 5 to get wherever you need to go. Great for bar hopping, but not for much else.
4. 200 sqft: imagine what this might be like for a second. It is smaller than that. The high ceilings help (the ceilings above both beds, however, are not that high, and it can get majorly claustrophobic), but half of the apartment is cut off by a giant wall and ladder to the loft that make it feel even smaller. The pictures do not show this well, which meant we were caught off guard. The additional sitting area by the brick is also way smaller then we imagined. So think small, because that's what you're in for. I'd say it's okay for two people (couple or otherwise) who are going to make a point to not be there often. Other then that, I'd avoid it.
5. heating and cooling: the AC worked just fine for us, which contradicts a few other reviews I read. The hot water, however, was a completely different story. We had no hot water :( which meant very cold showers. Unsure if that was an issue with the individual unit or the building as a whole, but that didn't help the whole experience.
Overall, the place was clean, the hosts were pretty communicative, but the place was definitely not for us. It was so bad that we left after our first night (we had booked 3). It was so cramped, we had to get out of there. Take our word for it - you can find a better place with some ahead of time planning.