If I were to ever return to Naples, I would definitely stay at Manuela's place. The apartment is huge - much bigger than it appears it pictures. The apartment met/exceeded everything that Manuela said about it.
It's extremely well located if you want to stay in Naples proper - it's merely a few steps from the main train station/metro line. We did quite a few day trips out of Naples, so the proximity to the transportation was excellent.
As it is in the heart of Naples, be aware that there is quite a bit of outside noise (honking cars, sirens), but the thick windows along with doors over the windows help to block most of the noise out.