Very, VERY basic. The dorm is a sports hall which has dozens of bunk beds chucked in, all in segregated areas of about 6 bunk beds, no pillows provided. The showers are communal so not for the shy or self conscious.
But don't let any of this put you off. The staff are incredibly friendly, willing to help you out or even just have a chat. There's free wifi and 2 PC's with internet access which are completely free to use. The bar is open 24 hours and very cheap. It is a stones throw away from a tram stop but everything is within walking distance anyway. I couldn't possibly comment on noise, quality of sleep etc, due to the fact that the bar is open 24 hours and very cheap, making sleep rather easy....
I highly recommend Travelers Hostel Ujezd for travelers, young people or just anybody looking for a place to sleep in a very social environment.

Don't come here expecting luxury. You'll hate it. However, if you are interested in finding a great place run by the friendliest people you will ever meet, a bar that is open 24 hours a day and the chance to make friends with people from all over the world, then I really couldn't rate it highly enough.

Hostel Ujezd is run by Honza and the gang in a sports hall that they take over for the summer. It's clean, but VERY basic. Everyone sleeps in one huge dorm, so privacy is limited and a blissful night's sleep is far from guaranteed. That's because people come here to have fun. The place, whilst mostly populated by the young, had plenty of thirty-somethings and older there too and everyone we met were both friendly and up for having a great time. It seemed that laods of people return repeatedly year after year, which I think speaks for itself.

Maybe we (husband and wife who had dumped the kids with granny for the weekend) were just happy to rough it for a few days here to remind ourselves that we're not ready to retire just yet.

Basic...but brilliant. And very central location for Prague Castle, Charles Bridge and the Old Town.