I have stayed here several times in the last eight years of various trips to Granada. The dorm beds are comfortable and quiet, all things considered. When I stayed last week, I opted for a small private room with shared bath. The room was miniscule with only one plug: I had to strategize between charging my stuff and using the fan (absolutely essential), though (really) no time was spent in the room, except to sleep. I like the relatively new shared kitchen facilities, though guests need better training at cleaning up after themselves in there. Seriously. Wow. I had to work at not "being that person." Backpackers: you're not at home. I've never ordered the breakfast that that is prepared here. DVDs available. Book exchange -- all the fixings of a terrific hostel with a lot of different choices for room: private, shared, with or without bathroom, etc. Good options at very reasonable prices. You can handwash laundry and hang stuff to dry on the third floor, or use the laundry service.
The folks at the front desk are lovely and very helpful. The swimming pool is also quite small; I've never used it, but understand the appeal (in theory at least) in the heat of Granada. The free wifi and coffee are awesome, of course. For the first time, I did the ride to Lago Apoyo for the day with the "sister" hostel El Paraiso (up for sale, apparently). This was a nice activity and cheap: $12 return ride. I'd recommend it. The only thing that bothers me about the Oasis is the cigarette smoking in the lounge -- there is not a lot of open, circulating air and so it's not very pleasant. The bathrooms need more maintenance, but are otherwise fine. Fantastic location.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.