Like other reviews have noted, the location is perfect. Easy walking distance to sites, kind of in the middle of all of these: Coliseum & Forum, Pantheon (really close), Trevi Fountain, Spanish Steps. Vatican is a short, easy bus ride away. The train station is also walkable (10 minutes), but it's so easy to just take the bus (which stops literally around the corner from the hotel). If you have a Roma Pass, the bus is free. Note: Hotel Giardino is not near a metro station, but the metro doesn't take you all the places you want to go anyway.
The staff was very nice and super helpful. Everyone speaks English. The room was unremarkable, but very clean and adequately appointed. The breakfast was more filling than I expected and a nice break from having to pay for every meal. It's really all about the location though. We took many night walks, and between the hotel and places of interest at night (e.g. Trevi Fountain, Piazza Navona) it is completely safe to walk around. I highly recommend seeing Rome at night!