The apartment is really "grand" in pretty much every respect: it's very spacious, with high ceilings and large living spaces, all modern appliances and comfortable bedding. It's super centrally located, just one block from the Charles Bridge.
The one thing I was a little confused about based on the description and looking at the pictures was the bedding configuration - there are not two double beds in the second bedroom, there is one double (or queen-sized) bed and one twin bed. And there is certainly plenty of room for additional guests in the common spaces, but not sure how comfortable that would be.
Another thing to point out is that the apartment is at the corner of a busy road and a not quite as busy side street. There are double windows throughout, which reduce the noise to fairly low levels when closed, but if you are someone who wants to sleep with open windows and doesn't like street noise, then this place may not be for you.
But overall I feel like we received an excellent value for the price we paid, we had a lot more space than we would have had in a (more expensive) hotel, and we were right in the middle of Prague, which is a beautiful city.