It was a tremendous experience in every way. Danilo was incredibly warm and welcoming. He was also very accommodating and provided lots of helpful tips. I can't imagine a better host. We stayed there for 10 days.
As for the apartment, one characteristic stands out: the view. It must surely be one of the most spectacular views in all of Prague, as you are looking at the Prague Castle--the largest castle complex in the world.
The location of the apartment is extremely convenient (you're right next to the Charles Bridge) and, while it can be rather noisy outside, the double-paned windows, when closed, entirely block out the noise, so it's not an issue.
The apartment itself was well appointed and very clean. The king size bed was very comfortable (my wife and I both have sleeping issues so this was significant).
Note that while the bathroom is small, that is common in Europe and we didn't find it to be an issue.
As Danillo has noted, it's on the third floor (thus the amazing view!), so you need to be comfortable walking steps. We didn't mind it at all.
In short, it was a tremendous experience and we would stay there again in a heart beat.
Thank you Danilo!