We spent five nights here, really lovely place!
The staff were kind, friendly and helpful, the room was well appointed, the location was great for accessing both more central areas and the castle (plus, it's 1min from the metro at malostranska),
Wifi worked great and the bed was very comfortable - although ours was split down the middle somehow - I assume a split mattress because it was so big? This did make it a little uncomfortable as a couple, avoiding the ridge! It was a very comfy bed to sleep in, though.
WELL worth getting the breakfast. SO good - and something for everybody (including us, we don't eat meat... but we had fantastic breakfasts every day). The food was great and we often lasted until the evening after filling up for breakfast :)
The bathroom and bath was great (although ours had a full glass door, a little embarrassing when you wished to use the toilet), with travel soap/toothbrushes/etc provided in case you forgot anything.
Had a great time, would stay there again in a heartbeat :)