This was a surprisingly spacious place in the heart of Trastevere (right by the tram stop on Viale de Trastevere) with a very comfortable bed! The wifi works great, the views are very pretty, and the only noise comes from the pigeons that roost on the roof nearby. It is on the 5th floor (counting American-style), which would be a bit of a hike if you're not in the best shape, but it's good practice for all the walking you'll do as a tourist in Rome.
We were there during the coldest part of the year, from New Year's Eve through Epiphany, and the heat worked great when it was actually on. The problem was figuring out how to turn it on—just make sure to get whoever lets you in to explain the thermostat in full, if it's cold out when you visit, or you might end up wearing sweaters to bed. I'm sure we could have figured it out if we'd gotten in touch with Emanuela, but to our discredit, we just poked a bunch of buttons and gave up.
Also, the plumbing in the building is a little smelly, with some strange odors coming out of the bathroom from time to time. Other friends who have stayed in other apartments in Trastevere have noted the same problem, so it might just be endemic to the centuries-old plumbing of the neighborhood—if it's not so cold, and you can leave the window open, it's really not that noticeable. And if it's not cold, this apartment also has some lovely little balconies!
And I'd argue that it's worth it for the neighborhood. This point in Trastevere puts you a 20- or 30-minute walk from the Vatican, the Pantheon, Monti, Testaccio, pretty much anywhere you'd want to go in Central Rome, and if you want to go further (or it's freezing out), it's right by a tram stop, and close to a bunch of buses (the public transportation in Rome is pretty great, at least from an American point of view). Plus, there's a great pizza/suppli spot right below the apartment (I Suppli), a great gelato place around the corner (Fatamorgana), and one of the best wine stores in Rome on the same block as the gelato (Les Vignerons). Great restaurants like Tavernaccia Bruno are just down the Viale (or down the tram line), you can walk to the food in Testaccio (like Volpetti, Piatto Romano and La Torricella, and the bakery Linari, which looked like it had the best fresh-baked aperitivi hour nearby, with good coffee and drinks to match).