This hostel at first glance is very, very dodgy. The hotels.com pic is severely outdated, as the door under the sign is misleading, and is shuttered down. It's instead a single door under the very right of the sign.
The area itself is horrible to look at. It looks dangerous, and is indeed a red light area. It's on the edge, and with proper patching, the red light area can be avoided altogether. 2 mins from Frankfurt Central Station, 40 seconds from a nice small market.
Hostel has no baggage drop area as the desk is a 2m x 1m box. Key policy is also a bit dodgy as its a "leave key with us when you leave" deal. I am not travelled enough to know if this is normal, so to me it was dodgy, but please make up your own mind. I must stress that nothing was missing from my room, and with the exception of things moved during daily cleaning, it seems as though nobody entered the single room I was in.
I had the chance to meet 3 staffers of the hostel. First lad I met, lovely, lively, gave me the run down of the area after my concerns were expressed, basically the don't talk to anyone and polite decline the women of the night. Other two were always silent and tired, one even sleeping on the night shift.
Room was kept clean, superb showers, clean beds, all looking new. No fridge, kettle or any other hotel quirks.
I would recommend a short stay, but I would not make this my first choice, despite a pleasant, trouble free stay. 5/10, bad area, dodgy first glance, great room.