It is a unique place. The original inhabitant, i.e., the father of the present owner, was -- if I understand correctly -- a theatre scenographer. The apartment has thus a really artistic feeling. You might want to invite your friends just to let them see. The bathroom is indeed equipped not only with a whirlpool bathtub, but also heated floor.
Pavel and his producer Zuzka took good care of us, responding to our queries, being helpful and flexible with both check-in and check-out. Zuzka's local recommendations in terms of shops and restaurants are really worth heeding.
Speaking of which, Žižkov is a very convenient area to live. We lived there for three weeks and we still did not manage to try all of those promising restaurants, bars, cafeterias and pubs! Some places are truly hidden gems (e.g., restaurants like Hanil, La Casa di Erminio or Porke, just to stick to the immediate vicinity); you'll find something for every taste and wallet size. Tenement houses in the area can be surprisingly beautiful and do try to see Kostel Nejsvětějšího Srdce Páně from the inside. Another tip: try walking or jogging to Riegrovy Sady and find the spot with an amazing view of the city centre. Especially in the evenings, crowds are gathering there for picnics just to enjoy that sight. About the only problem that may irritate you are occasional dogs' excrements on less than perfectly lit streets. But in terms of safety and security, I didn't notice any real issues. Some locals told me that Žižkov has greatly improved in last 15 years or so.
Contrary to what you see in other reviews, the place has a hair dryer and blinds (if slightly prone to getting stuck at times). Contrary to the description, I somewhat doubt if a group of five people would survive long in the apartment, unless perhaps for one or two nights (and with two pairs happy to share their beds). Even sharing a meal together for at least two people may sometimes feel cramped. But overall, a single or a pair can happily stay in this apartment for weeks and leave Prague with very good memories.