Definitely a hostel. After a few days of exploring the space I actually began to really enjoy it more but the initial first day I was thrown off a bit.
The common space in the 3rd floor is really cool and if you're heading into it knowing it's the hostel the experience is actually pretty cool.
Aside from that the guy who does the night shift duties kind of pissed me off the first couple days - definitely lectures more than he gives guidelines. By the 3rd day I actually started enjoying him though. He apologized for something's that had happened and I got that he has a bunch of responsibilities but I wish his approach was guiding more then lecturing.
The bed space was very hostel like - shared, bunk beds, low key. Be prepared to be in a shared environment.
Common areas: the down stairs has a cluttered feel but has it's charm... Kind of, definitely within site of the homeless outside, the upstairs was cool though, felt like a place I'd build a pillow fort and listen to music.
All and all for the price is pretty good for the setup as long as you know you're in hostel located where the hippie movement started. Great location when you step out of the Haight district right next to the park and in relatively center SF.
Would I stay again? Maybe. Depends what kind of trip in trying to go on.