Absolutely brilliant. We stayed at the apartment owned by the hostel. There's a view of the Collesium. It has a little lounge, bedroom, kitchen, dining room and a great little terrace ...stay there? I'd like to live there! Nicely done out, modern but authentically 'roman'. Perfectly clean, great service form the owners including lots of tips for restaurants etc. No more than a five minute walk into the main tourist spots. At just £45 each, it's only a bit more expensive than some of the hostels but is a huge step above.
Fantastic option for couples. HIGHLY recommend.