Jonas was a fantastic host. Extremely nice and very responsive. He responded within minutes to most of my requests/questions while I was there, and within 24 hours leading up to the trip.
The apartment was as-advertised and there were no unwelcome surprises. The location was a huge selling point. It's right near the heart of things in Beyoglu, but on a side street that quiets down at night. Istiklal and its food and shopping are just up the hill, there are many neighborhood corner stores, a supermarket for bigger needs and cafes everywhere within walking distance, and a five minute walk down the hill takes you to the tram to Sultahnamet (about a 15 minute total trip to get to the old city from here). Be aware that like much of Istanbul, it sits on a large hill which can be daunting after a long day of walking (but funicular can be taken from near Galata bridge to get to the top, in which case it's a walk down to the apartment).
All in all, a great experience (I stayed for one month) made better by a great host. Highly recommend.