The apartment was really great, I can't really say a bad word about it! First of all - it is large, functional and very nicely designed (well, maybe apart from the chandeliers, but I can forgive such a detail ;) ). Second - although the apartment is close to many tourist attractions and the streets are full of cars, it's very, very quiet! I didn't realize it could be noisy outside, until I first opened the window. Third - the air conditioning works really well, it is in every room, so it's very easy to maintain and regulate the temperature. Fourth - the apartment is not very bright, but has so many light sources that it doesn't bother at all (and I am the person who really pays attention to it).
When it comes to the equipment - again, I can only say good things. I was able to sleep on one of the most comfortable beds I've ever slept in and use such a large shower that a family of 4 could use at the same time. The kitchen is also really well equipped - I guess the only thing you can't do is bake a cake or mix fruits (but who would do it in Italy!).
The location was AMAZING, I couldn't imagine a better one. I was not going to see the Colosseum, but all the other attractions were so close, and walking was such a great experience that for 2 weeks I didn't use public transport even once. There is at least one supermarket nearby and a pharmacy right outside the door of the building, so everything you need for a "normal" life. There are also lots of really nice places including one of the best gelateria I have visited in Rome (recommended by the host Gelateria La Romana), a bakery with a great selection of breads and cakes at really good prices (Il Gianfornaio) and a small family restaurant with a really great traditional Roman cuisine (Su & Giu Cucina Romana - I don't know why it is not recommended by the host, but it should be!).
Luca was great. He answered to the messages almost immediately. I had a few problems during my stay (e.g. no hot water due to a power cut) and Luca was always there to solve them. He also always answered my questions and suggested lots of nice places to visit (both in person and through the little guide he did for the guests).