My friend and I stayed at the Klub Habitat hostel in Prague for 4 days at the beginning of May. The location is quite good, you can reach the pedestrian area and the river within a few minutes. A huge supermarket is nearby too, which is really handy. The hostel was fairly clean (they do change the sheets regularly!) and our room (shared with 3 other people) was nice and spacious. The staff were friendly and helpful and you get free internet access. Don't know about the breakfast (included in the price- about 16 Euros), we never made it there... (good nightlife! :-) ). You should definitely lock your belongings away downstairs (free lockers), not doing so is really unsafe and irresponsible. We had a really good time in Prague and I'd go back to this hostel.