We stayed with my family at Ubeydullah. The flat is exactly as described. It is perfectly located, just a few steps from Taksim Square and all amenities (public transport, supermarkets, Istiklal Street etc.).
Ubeydullah is a very good and helpful host who was in regular contact with us before and during our stay to see if everything was going well and to give us some advice.
I would recommend this flat and would definitely book Ubeydullah's services for my next stay in Istanbul.