One of the best experiences I had staying in Prague so far, I'm sure to come back at some point. The team was very helpful and had very good suggestions for going out, which is awesome if you are not here just for sight-seeing but also things of the beaten tourist path.
I can't say much about the breakfast since I always slept through and was too busy with my friends to take advantage of all the other amenities they offered.
It is a hostel, a lot more easy going and personal than most other places. If you are planning to go out and don't need an overly luxurious stay, I can wholeheartedly recommend the Hostel Elf. Even if you usually go for something more luxurious, I'd still recommend it, because that is how I think Prague should be experienced.