Our family had a fantastic 4 night stay at Mr. Frills. The room was a double plus 2 singles in the loft. Our room and the common areas were clean and nicely furnished. The wifi worked well. The breakfast is self-serve, nice if you want an early start, and more than adequate - coffee, tea, juice, milk, 6 kinds of cereal, brioche (croissants), jellies, bread. The building has an elevator.
The location is great starting point for exploring Rome. If you prefer walking, the Colosseum is 20 minutes away, the Basilica di San Giovanni in Laterano is 15 minutes away. Public transportation is fantastic, metro stop (line A, one hop from Roma Termini), bus and tram are all within 2 blocks.