We stayed in this apartment from June 17 through June 23, 2011. We are a small family with twin boys, aged 8. The listing is right on. Everything in the pictures represents this property exactly. It is a great size for us. The alleyway is lovely and quiet, compared to the city. When we were "home" we had the front door open, allowing both light and air to pass through and it was so pleasant. The neighbors are an older couple, and though they don't speak English, and we don't speak Italian, we exchange pleasantries each day. It is very secure with solid wooden doors that you close and lock when gone, and at night. When you exit the alley, you are immediately in the maze of narrow cobblestone streets that is the destination Trastevere. Tons of cafes/restaurants right here. Many travel books suggest that Trastevere is "crusty" or a bit dicey, but it is not. For better and for worse, it is completely safe and touristed.
The apartment is clean and simply furnished, the kitchen is simple (like in other big cities we have visited), and it is all Ikea-like.
Now, the downsides, which for us are not enough to choose against this apartment: no washer. Our clothes are pretty toasted (little boys who like Chocolate Gelato). So, remember to bring washing detergent for hand washing. The weather is warm and the clothes could dry outside, but it would help to have a drying rack. ( everyone else in the alley lays out things to dry on racks). The nearest grocery store that we could find is a 10 minute walk, which is ok, just had to haul the bags back.
I would absolutely recommend this property to friends. Rome has a lot to offer, and you can walk to almost everything that is "classic Rome" from here. We do recommend the Rome Pass, if you really want to see the colosseum, because you can literally walk right past the very long line, and go in the "rome Pass" entrance ( to the left of the line). Then, we used it for our public transportation, as the boys cannot quite walk as much as we could.