I stayed here for the 2nd time, with my wife now. First, I will mention couple of things you need to expect.
My wife straightaway found small ants which were annoying her (I was not noticing them at all. Ceren sent a cleaner to do a deeper cleaning and told that she will find "germs"-control team after we leave, but this is an old house it may be a difficult).
Also it was a bad luck that just in the beginning of 2nd stay the boiler partially broke down, only the radiators worked but no warm water, wife was disappoited again. Ceren was trying to solve it ASAP, due to several issues we had to wait for a few days.
Be ready for the high hills in Besiktas. As well the toilet is on the 4th floor, may be difficult for some people.
All the rest is just positive:
WiFi is good enough, big fridge, washing machine, dish machine (I didn't use), iron, hairdryer, projector, enough space to accomodate 4-5 people (but in the kitchen only 3 will fit), responsive host, very good district in general.