I stayed at the World House in Feb 2010. The hostel's location is excellent: incredibly convenient for seeing the major sights of the city and going out at night. The condition of the rooms was acceptable, but the dilapidated condition of the bathrooms throughout the hostel left much to be desired, no matter if you get a room with a private bathroom (icky and rundown) or in the dorms with shared bathroom (even worse condition).
That said, the price is really low and the staff were very friendly. So I guess you get what you're willing to pay for.
I enjoyed my stay in Istanbul but will stay somewhere else next time. More