I spent three nights in Rettifilo appartments in April and I can recommend this place - room was very clean and cleaned every day, bed and shower were comfortable. A minor issue with warm water was fixed by Gianluca in 5 minutes and never re-appeared.
The only thing you should keep in mind is that the place is on the first floor and most rooms are overlooking pretty busy Corso Umberto I street - if you are not deep sleeper, don't forget your earplugs. With them put on, I enjoyed fine sleep, despite that I often struggle with it. From what I could see from the plans, Stanza 1 is the only room with windows to the smaller street. The place has very good location, 10mins walk to Porto di Massa bus station and 20mins to the centre.