Stayed at a place called Hotel Gea Di Vulcano just off the Via Nazionale booked through Booking.Com.
Its within walking distance of the Termini but well away from any dives and on the right side of town. Its fairly central with all sights in walking distance and couldn't be faulted for cleanliness etc. Quite reasonable prices as well. Excellant Pizzaria on the corner of the hotel building.
Book in advance for the Coliseum, available through the Rome Tourist Board to avoid the queues (sorry don't have the link).
Don't miss the Pantheon, and call in at the El Greco Cafe at the bottom of the Spanish Steps in the street with all the expensive shops for a belting Cappuccino if you like that sort of thing. If you want to do the Vatican museum get there really early - we queued for well over an hour arriving about half an hour before it opened and it was November.
I also managed to fit in a Roma game - they got stuffed 3-0 by Udinese. Their Ultras were not best pleased and set fire to their seats