The Vatican Museum was a bit disappointing. The Sistine Chapel was crowded and hot. We only spent a few minutes there. St. Peter's blew me away! You could easily lose a day in there, but we limited ourselves to about 2 hours.
We thoroughly enjoyed Piazza Navona and the Pantheon. Other highlights included the Church of San Clemente and the Borghese Gallery. Trevi Fountain and the Spanish Steps are so packed with tourists and vendors selling junk that you can't move. The city of Rome really should crack down the rose vendors - they are beyond pushy! We were extremely glad we did not stay near the Spanish Steps. The sidewalks were full at all times of the day. We couldn't walk and just kept bumping into people.
We liked staying away from touristy areas, although in Rome, us tourists are everywhere! We got a big kick out of the little shop next to our B&B. This little place had everything you needed: beer, wine, cheese, meats, and snacks. The old guy would sing as he prepared our sandwiches, which my wife adored.
Quick Tips:
We spent 1 night at Castel St. Angelo, where they had all kinds of activities going on: dancers, acrobats, and most importantly, a bar. We took it all in while enjoying beautiful views of the city.
Best Way To Get Around:
We walked everywhere but the Vatican.