I was only here for a Wednesday evening, but it was surprisingly quiet given it is a street-level walk-in in the Trastevere. Location is excellent if you're in town for a night or a few days hitting all the Trastevere has to offer.
This probably isn't the right apartment for you if you're staying for a week or longer and plan to spend a lot of time in the apartment - mainly because you'd likely want more space and a bit more natural light.
Location is also great if you're not spending all your time in the Trastevere as most highlights are a quick walk away.