The apt. is about 10 min. by foot from Leidseplein, and about 20 from the town center (we never used public transport and walked by foot to every place in the city).
We were a group of 4 staying in the apt. it wasn't large, but there was enough space for all of us...
It should be noted that the apt. is on the last floor, and reachable by a narrow staircase. The climb is doable, but not always easy. Also - all the closets and drawers in the apt. was full with the hosts stuff. Not a problem for us - but could be for people who would like to store their stuff in closets and not in their suitcases.