I'm a bit surprised to read that many bad reviews. Maybe I was just lucky the night I spent there.
First, every place in the hostel was pretty clean to me, including the showers/bathrooms. Had no hot water problem there, I didn't even remember the "push" button.
Had a 3 people room to share with a German and a Brasilian (both real friendly, we had very interesting discussions and shared a lot). We had plenty of space and the bed was OK, clean enough and I slept really well. I admit it's a bummer to share a key for the room, but it didn't cause me any real problem.
The breakfast was not extraordinary I admit, but it was good and filling (one large piece of bread, jam, and bottomless coffee, chocolate that was OK). You have so many cafés in town so if you want a better coffee, you know what to do...
With a cheap rate like that I was expecting the worse, but I think I got plenty for my money. I remember that it was the cheapest you could get in Paris I think.
One negative aspect : their web site sucks and hasn't been upaded for years. They should have on-line reservation or at least make it possible to book on other websites such as -------.com.
It depends on your expectations for an hostels, if you can afford it, go to a fancier place. I had a great time there and experienced much worse places than that. Moreover, I think that many hotels in Paris are more expensive and much less clean than this hostel. I'd go back there next time.
Another thing : why would someone want to take a nap in the afternoon in Paris ???? Come on ! You have all the rest of your life to sleep, back home ! Don't waste your time sleeping while in one of the most beautiful city in the world ! What are you ??? 70 years old ?