I had a very good experience at Umberto's apartment. The views are the real deal, you get an un-protruded view of Mount Vesuvius, as well as the city of Naples at large and the Gulf of Naples. The place is very clean, it appears it received a renovation in the last few years or so. Nice bathroom, bedroom, and kitchen. It's cozy, perhaps small, but I thought it worked just fine. It can be a bit hard to find from Stazione Centrale, but you'll get the hang of making your way around the city after a while.