Went to Istanbul for the first time, and had a great stay at Isik's place!
The communication was outstanding from the start.
Isik (in fluent English) explained everything and was always close by and reachable.
His Istanbulkart (for travelling on all public transport in Istanbul, and easy to 'refill') helped us out a lot.
(RECOMMENDATION: Get the €10 sim card right away from Isik - you'll have 4g internet throughout the stay, very useful, espacially for non-Turkish speakers getting around town - a great deal from our experience)
Located in a small street just 100m from the very lively Taksim Square, Isik's place is still very quiet. There are a variety of shops and fast food places around as well as money exchange offices.
The air-conditioning was a lifesaver + free WiFi and nice little kitchen.
There is a washing machine, TV, iron and iron board as well as fresh towels and bedclothes.
On the way to the airport (Sabiha Gokcen) we used the Havabus which is just around the corner.
All in all, a cozy place with perfect location and great dedicated host.