Very clean apartment, modern furniture, perfect location in my opinion.. walking distance to Galata, Taksim, others.. easy metro ride to Sultanahmet..
The larger apartment fits up to 4 people and the smaller apartment up to 2 people just fine for sleeping.. not spacious enough to hang out all day there..but who would wanna hang out in the apartment all day when you're on a vacation to Istanbul anyway?
The host is very reachable and responsive.. I'd definitely recommend staying there..