The apartment we originally booked was unavailable due to technical issues, so Jan offered us a replacement apartment for the same price (one of his apartments in Polska street), which was really great.
But that's why we can only rate the apartment at Polska street, not the original one at Legerova Street:
The location is good, a metro station is just around the corner. We didn't use the metro but walked: 35min walking distance to the city centre (astronomical clock) and ~one hour walking distance to Charles Bridge.
The apartment itself was equipped with everything we needed. There had been some issues, though, like the showerhead was not installed/usable and the cuttlery had to be re-washed before use.
We spent 2 nights in the apartment, so it was okay.
Jan was on vacation before and during our stay, but we weren't informed about that until we finally reached him via phone call only some days before our departure. So the communication before our trip was complicated, but he was available and replied really fast during our check-in/out.
All in all we recommend the apartment and Jan as a host.