My girlfriend and I stayed at the Happy Holiday B&B for 4 nights during New Years in Rome, and found it to be an adequate place at one of the busiest times of the year in the city.
A very important thing to note about this hotel: If you are planning to check in early (before 10ish) or late (after 6ish) it is likely that there will be NOONE available to check you in. Phone ahead (best from the airport since there aren't any public phones nearby).
So here are the basics of the hostel. It is run I think by a family, of which Nicolas seems to be the main guy. He is very helpful and nice, will show you major sites on the map, and will go out of his way to help. If you arrive late in the evening, it is him who you will likely call to be let in. The family lives near the building and thus can arrive within about 20mins after you call. The other person who helps run the front desk I presume is Nicolas Sr. He is nice also, though doesn't speak English and smokes a pack of cigarettes a day in the lobby (which floats into your room without difficulty). I think they own rooms throughout the building but the main place was on the 4th floor.
The Hostel itself is across the street from Giovanni church, beside a small parking lot. There is a big door at street level which you need to give a meaningful shove to enter into, and then proceed to the Left side, up some (~8) stairs and take the small elevator to the 4th floor (I think). To your Right will be a door marked Happy Holiday B&B. If you are lucky it will be open, if not call the number and wait. Don't ring it multiple times, the manager is not there and you'll just wake everyone up.
The room we had was a private room of regular hotel size. It had a dresser, safe, and the standard European two single beds pushed together to magically form a double. There was a bit of a view into a common courtyard, but was nothing to write home about. It was also heated and was cleaned each day. The lamp was cool.
The bathroom is shared by everyone. For us this meant maybe 12 people to one bathroom, which wasn't the greatest thing in the world but we managed. What saved us is that we woke up early and got showered and ready before everyone else and thus avoided the morning rush. The bathroom was clean though, and there is a big ol' common bottle of shampoo for you to use. Also you are given towels.
The breakfast consists of juice, bread (which you can make toast from), and some pastries. The condiments are chiefly jams and fruit based spreads though there were some Nutella packets when we first arrived. You can also make yourself coffee or tea. This is not a very decadent or luxurious affair but you can't expect it for a budget price.
There is wireless internet and a computer provided for free, but the internet stopped working early in our stay. Luckily there was an unsecured wireless network that we could use. Thank you DLink.
At 80 Euros a night it was actually pretty expensive to stay here when comparing to some of the other places we stayed throughout Europe, considering that it is a hostel (despite the clever name). However we stayed during the busiest time of year in Rome so maybe that had something to do with it.
The location was fine, it's about 10 minutes from the San Giovanni Metro station or 20 minutes walk from the colosseum. Two blocks towards the Colosseum on the right is a good little restaurant with a bunch of weird stuff on bookshelves. The Bruschetta is great.
Overall, this is a hostel that happens to also provide bread and juice. If that makes it a B&B so be it. Paying 80 euros a night and sharing a bathroom was disconcerting to say the least, but Nicolas is a good guy and the place is in a good area. I would recommend this place to students and young persons looking for budget accommodations (if it is the cheapest), not to families, older couples, younger couples, or those with mobility issues or light sleepers. Again, just so it's clear....this is a hostel, but it has some charm and we enjoyed our stay apart from the bathroom.
