Andrea's place is as-advertised: literally down the street from the Colosseum. You may feel yourself beginning to take it for granted after seeing it so frequently during your stay. Do not let this happen. It's incredible.
Anyway, we were traveling to Rome from Pompei by train. We arrived at the Termini station, and opted to walk to his apartment. Only took 20 minutes and it was an easy, gorgeous walk. We later found out there's a rail station immediately next to the Colosseum. This makes virtually anything in Rome accessible from Andrea's place.
The place itself is housed within a delightful neighborhood - you always feel safe in and around it. There's a great 24-hour market around the corner. The apartment is nice - no complaints about it. We slept well, felt clean and comfortable, and had an overall great experience.
It's worth noting some of the best pizza I've ever had was at a restaurant around the corner called "Coming Out." Awesome staff. Elect to sit on the street so you can enjoy people watching and the view of the Colosseum while you enjoy your meal.
Andrea was a great host. He provided great and succinct advice and did a great job of making us feel at home. When we return to Rome, I hope Andrea's place is available!