I had 2 night at Czech Inn - both nights in a mixed dorm. Even though we were many persons in the room, it didn't feel like that since the room were divided by a half wall so it almost felt like two rooms in one.
The upper bunks are high (= more privacy). At all beds there are a personal box where you can lock in values if you bring a lock. In there is also your own power outlet so that you can easily charge your phone without having to look for an un-used power outlet. Under the bed is also a box with enough space for all your luggage.
All the staff members were super friendly and helpful. All facilities were clean.
It was easy to reach the city by foot and there is a tram just outside the hostel as well, so it is also easy to get around in that way, I think (I only walked though). I will stay there again if I come back to Prague.