My husband and I stayed at I'zaz in July for 6 days and 7 nights (2 nights in the Ground Floor Apartment and 5 nights in the Balcony Apartment). Although the Ground Floor Apartment is quite small, it is clean and comfortable while the Balcony Apartment is spacious and just lovely. The lofts are just like their website portrays them: Airy, flooded with light and modern. The location is fantastic, a 2 min walk from Istikal street and right next to a lovely market where my husband and I would buy breakfast (honey, kayak and bread with fruit and veggies) and eat in the rooftop kitchen/dining. The main attractions are a solid 30 min walk, however it is much more pleasant then taking the tram (which is also closeby) as you discover hidden gems along the way. If you aren't too tired from exploring all day you can step out and walk to Galata Tower (5-10 mins) to enjoy Turkey's nightlife. The staff is friendly and accomodating and provide you with a real sense of privacy, as if you're living in your own awesome apartment in Istanbul.
My only hesitation would be the spiral staircase, might be a trek for older people and perhaps troublesome for little children/babies. Another guest felt it could get loud at night, but we were never disturbed.
All in all, we can't imagine staying anywhere else in Istanbul and you won't go wrong with I'zaz!More