Antonio's place is very nice indeed. First of all, it is located in Nisantasi - very central, beautiful, stylish, safe and lively area of Istanbul, which I love very much. Moreover, it is very close to many transportation options including bus stops and metro station. You can walk down the street to the Besiktas ferry station in 10-15 minutes or so. Eating out is not a problem - you are literally in the middle of HUGE variety of restaurants and cafes with lots of options for breakfast, lunch, dinner or simply a drink or two in the late evening.
The place itself has sufficient space for two people to stay without problems. Nice wardrobe in the bedroom with lots of hangers (very thoughtful!), comfortable bed (with relatively harder mattress, which I definitely prefer). Many other storage possibilities, so ever longer stay would be perfectly comfortable. Very comfortable sofa in the living room; air conditioning in every room is provided. We were there in wintertime and it was warm and cozy inside.
Kitchen is fully equipped with practically anything you may need including appliances (we didn't use any of them though, except for boiling some water in the kettle). Bathroom is nice with rain shower and good pressure of water, some improvement in bathroom lighting would be very much appreciated.
Big table provides a lot of space for dining and working, however working could become a problem in the evening hours, when noise from outside restaurants and cafes becomes really loud. Windows are protecting well, but it's still too loud in the evenings to concentrate on smth (headphone may help, I think). It's not a big deal though for those who are in Istanbul for leisure and entertainment only.
The place is located on the second floor, so you will need to climb rather steep winding stairs - not too many, but probably still something to consider for those with mobility problems.
Check-in and check-out was smooth and easy. Communication with the host -- effective and fast.
All in all we liked our stay very much, and we would definitely come again to continue exploration of our favorite city. Thank you, Antonio!