We stayed at Zero 6 for four nights. The owner, Luigi, was available to greet us on arrival at 1am following a delayed flight. He settled us down in a large, comfortable and newly renovated room, making us feel very welcome.
The room was clean, with very thoughtful extra complimentary touches, from a Nespresso machine to breakfast brioches and a soft drink-stocked refridgerator. The facilities were great for travelers --- there were USB chargepoints by the bed, free Wi-Fi and (a huge necessity for me!) a decently powerful hairdrier! The room was cleaned daily
The area was well connected -- around the corner from the metro and serviced by a number of buses. We were able to get back by bus from Centro Storico at night in under 20 minutes, and felt very safe doing so. It is super close to the Vatican city as well, so making it before the morning queues is very easy.
Luigi was kind enough to ease the check out for us as well, and we were able to take our time leaving on the last day -- that was the icing on the cake of a wonderful stay. Would definitely recommend and definitely return.