I'll try to remember to write more about Rome, but I'll throw in a couple things first.
Watch yourself in the Piazza Navona. It's super famous and very beautiful, which also means it's a huge tourist trap and a theives' paradise. I had two very good friends live in Rome for a year and they told me flat out to avoid walking across the middle. It's like walking across a minefield of pickpockets. The classic trick is for little gypsy kids to come up and beg while one of them snakes your wallet. Also the restaurants on the Piazza aren't that great. I'm not saying don't go there. I'm just saying be on your guard.
The Castle Sant'angelo near the Vatican is really cool. Also be sure to walk up to the garden above the Spanish Steps, the Villa Borghese.
St. Peter's is really beautiful, but I also went to the Chiesa de Gesu. Despite the fact it was being renovated and half the church was covered in scaffolding, I thought it blew St. Peter's away.
http://en.wikipedia.org/wiki/Gesu
Also don't forget to walk down the Appia Antica just outside the main city. It was the main road into ancient Rome and is filled with ruins, beautiful villas, stunning views of the Roman countryside, and Christian catacombs.
Restaurant report to come later. Best cuisine in any city I've been too. Cheap, insanely good quality, and a different dining culture. Skiaholic is right, it's the best pizza I've ever had. I literally didn't eat pizza for 6 months after I got back. I only had one or two pizzas there over the course of a week and it spoiled me that badly.