I can recommend Antica Residenza del Corso as a lovely alternative to a hotel in Rome.
Frederica (manager?) really made our stay easy in every way. Frederica contacted us - initially through expedia and helped us with airport transfers, directions and clear instructions about arriving after hours, and extensive advice on local restaurants/bars suitable for every meal and time of day.
It is located centrally in Rome just off Via del Corso in the middle of a fashionable shopping district, within walking distance of wonderful restaurants, bars, tratorie, osterie, bars, bakeries and many of Rome's famous sites e.g. Pantheon, Trevi fountain. It is also great for every form of public transport.
The room itself was quiet, clean, and comfortable. It may be a little uncomfortable on a really hot day, which we did not experience but there isn't great air circulation.