I stayed 3 nights at Sergio House.
First impression was very positive: hotel owner was kind and friendly, room and bathroom clean. But at the end of my stay I also found negative aspect.
I will try summarize the good and the bad:

Good
- position: 100 mt from Termini rail station (wich is also the main bus stop and metro station in Rome)
- price: payed 70 eu/night for a double, cheaper than similar accomodations
- kitchen availability: freely usable, equipped with burner and fridge
- courtesy: all the personnel was cordial and helpful

Bad
- room tidying up: in 3 days no one ever cleaned the room, nor made the beds
- light leak: since the hotel is located at the ground floor and the quarter is not so safe, window-shutter are permanently closed (locked with a chain!), so don't exepect a bright place
- noise: maybe because of thin walls/door, but in the morning I never waked up by myself: I was "helped" by room neighbours
- shower: as I wrote, (the two) toilets are clean, but only one has the shower and it's a basis-free one: water falls straight on the floor (and on the toilet seat)
- luggage: if you will need, as I did, to leave luggage for some hours, you will have to pay 5 non-negotiable euros for each piece. This is not my first stay in a hotel in Rome, but it's the first time I have to pay for this kind of favour

My overall rating is 3; advice is to choose it if looking for something cheap and well located as a starting point to visit Rome, but not for a relaxing vacation.