The apartment is very cozy, but it includes everything you need during a vacation. The hosts are genuinely warm and casual; we really felt welcome, ever since the first moment we met. The location is excellent for exploring the city – you have very easy access to a subway station and three funicular stations (we didn't use surface transport at all during our stay, so I don't know about buses).
Besides that, Vomero (the neighborhood) is probably the best as a home base for exploring the city – it's one of the two upscale neighborhoods in Naples (the other is Chiaia), and it's also very pedestrian-friendly (just walk up to Vanvitelly square and turn left on Alessandro Scarlatti). So even if you're tired after walking all across town, you still have a friendly neighborhood to chill out in the evening. We honestly loved everything about Arianna's, and we had a wonderful (first) time in Naples.