The apartment is large and comfortable - main bedroom, second bedroom/study, bathroom with shower, living (large lcd tv) and dining areas, and compact kitchen (basic kitchen appliances and tools). The place is light and airy in the morning and evening, remaining cool with the windows shut in the middle of the day.
The Trieste neighborhood has plenty of shops, an open air market, and restaurants nearby - the most important being De Angelis, home of the amazing "cremolato", a frozen coffee-not-quite-ice-cream desert. The great park Villa Ada is a short walk away. The location is perfect for getting around to any of the ancient sites of Rome and downtown. The 63 and 83 buses stop right outside the front doorway. The one detraction is a maddening flocking of loud (VERY loud) birds early in the morning, but this of course is no fault of Marco's, but is worth mentioning for those light sleepers.
Marco is a very attentive and responsive host, I would definitively go back and I recommend his place to anyone staying in Rome.