Just got back from Rome. Orso 80 is indeed great--do remember to order the antipasti and that the antipasti is HUGE--lots of plates.
Another restarant that we liked a lot is just off Plaza Rotunda--the Pantheon Plaza. It is called Armando al Pantheon. Great quality. Ask for suggestions--they give good ones.
Tazza del Oro for coffee. San Crispini ( near Trevi fountain ) for Gelato.
The Scavi Tour under St. Peters is amazing--you have to pre reserve and it's not easy, but really worth it!