I have just returned from 4 weeks at Gemma's apartment and loved everything about the stay. It came fully equipped with everything I needed and more - from a wide variety of cooking utensils to coffee maker to washing machine. There were even some food staples left in the cupboard for when you first arrive.
The terrace is an amazing space with unbelievable views. Of course, you have the gorgeous Basilica of Santa Maria Maggiore on your doorstep but you can also see the Colliseum & even San Peter's not so far away.
The location could not possibly be better - walking distance to all the major attractions, surrounded by cafes & restaurants, supermarket just across the piazza, and the main train station just 5 minutes away.
I would not dream of staying anywhere else when I'm next in Rome.