I just stayed at this apartment with 4 more friends...I'm not sure why the info is incorrect- It is Podwale 9 (and not 4) and belong to P&O Apartments.
We had a really great time!!! The apartment is very nice with a big & comfortable living room and AMAZING location in the Old City:)
The bads in the 2 rooms (for 4 people) were very comfortable!!! The open couch ( for the 5-6 person) is not so comfortable but also not too bad (its an Ikea couch).
It is not a 5 stars hotel but I really recommend that...next time I'm in Warsaw withe friends or family I'll go there again.