I stayed at Perez's apartment from June-mid August 2015. First of all, Perez was a fantastic landlady. Upon my arrival, she took me around town, showed me where to catch the buses and helped me set up my cel phone service. Throughout my entire stay she was always available by phone to answer my questions. Whenever there was an issue with the apartment- for example the hot water heater needed to be repaired during my stay- Perez was alway super prompt in getting it done.
The apartment itself is exactly seen in the pictures. It's comfortable, quiet (you can start to hear buses outside the window on weekday mornings, but that's true for everywhere in Nairobi), and secure (gated, with 24 hr watchmen). The WIFI is fast, the water is hot, there's a washing machine in the apartment and clotheslines outside the door, and there are plenty of tv channels to keep you in touch with what's going on in the world. It seems to be mostly professionals and families who live in the apartment complex, which was great.
The location is about a 12 minute walk from town (or a 5 minute matatu (minivan) ride), and an easy 7 or 8 minute matatu ride from Westlands, making it very conveniently located. Matatus can be caught directly in front of the apartment. In the immediate vicinity, there's a grocery store, a couple of restaurants/bars, and a fruit/veggie market, but it's not the type of area you would have reason to spend much time in, except to buy your groceries or grab a quick bite to eat. It felt safe to me; I often walked home alone at night, but I am a large man, and people generally would not recommend doing such a thing. During the day no one has qualms about walking around the area whatsoever. I never felt threatened walking about anywhere in Nairobi, really, (except for occasion run-ins with the military in town, who attempt to extort travelers if they don't have a photocopy of their passport on them- be forewarned!).
All in all, I had a great experience and would certainly stay here again if/when I come back to Nairobi. Perez is a fantastic host!