In short: if this apartment is available, book it!
We had a great time in Rome! The apartment is just lovely and very comfortable!
Renato's co-host, Michele is just amazing. He is very communicative and will assist you in every possible way!
You can get to the Colosseum by foot in just 10min. The Vittorio Emanuele metro station is also near by and the Bus line 70 is even closer. From there you can explore the entire city.
There are also good restaurants in the crossing with Via di S. Martino Ai Monti.