We had a really great time at Diego's! We spent 5 nights there and were very pleased. It really is in a great location, just a 10 minute walk from the Colosseum and right next to the Metro that takes you anywhere else. The place itself is very clean, located in a quite neighborhood right off the center (not icky like the places near the roma termini)
Diego had been really nice and accommodating, gave us some good tips on our first day and was quick to reply to anything we asked.