Just an excellent place. My partner and I stayed here for NINE nights in a row, it was so good: we made it our base of operations for visiting the entire Bay of Naples area. It's just so centrally located: 5 minutes walk to the Pompei FS (i.e., official state) train station, 5 minutes walk to the Pompei Santuario Circumvesuviana train station, and 10 minutes walk to the alternate south-eastern entrance to the ancient site (which is a FAR less crowded entrance than the other, more main, entrance to the site, the so-called "Porta Marina" entrance at the western end of the site).
With this hostel's amazingly convenient proximity to the trains, you can just stay here instead of in (much more expensive and much more dangerous) Naples, and use Pompei as home base. You want to visit ancient Pompeii itself?--just 10 minutes walk away. You want to visit ancient Herculaneum?--just 25 minutes away on the Circumvesuviana train. You want to visit Naples itself?--just 50 minutes away on the Circumvesuviana. You want to visit Sorrento?--just take the Circumvesuviana in the other direction. You want to visit ancient Paestum (DO NOT miss this awesome day-trip!!!)?--just take a train to Paestum from the FS train station in Pompei; Paestum is only 1.25 hours away on train from Pompei.
And the hostel itself is just a pleasure: Clean (there is even maid service which cleans your room every day or two!). Nice layout (rooms clustered around a central fountain area, reflecting the layout of the convent which this hostel used to be). Cheap cheap cheap! Yes, noise can be a problem, if others want to hang out and drink/chat all night in the central courtyard (though earplugs solve this problem immediately); but we were here for nine nights in June, and only encountered noise problems one night during our stay.
Yes, the breakfast is a bit stripped-down. But what does one expect in a hostel? Besides, the rooms here are so reasonably priced, you can buy a full breakfast elsewhere with all the money you're saving and still come out well ahead in the deal.
To sum up: You want to visit the Bay of Naples area on a budget? Great. Just don't stay in Naples itself. Stay here in Pompei.