We stayed with our baby daughter for 4 nights in the apartment and it was a great experience.
The apartment is very conveniently located, close to the Colon metro station (direct link to the airport), it's in walking distance to shopping areas and to all the attractions in the center. Unfortunately we didn't get to see much of the old center during our stay, as we went to the zoo, aquarium and to the beach (all are easily accessible by metro or direct bus link from the apartment), but we did visit the Valencia Cathedral which is in walking distance.
The apartment is nicely decorated, and has all the amenities, including some sweets and water left for us that were a very nice touch.
Next time we're in Valencia we'll definitely come back.