Derin's place was the first place I stayed in my month long trip to Turkey. I couldn't have asked for a better place! The apartment is spacious for 1 person, clean and has everything you would need for a longer stay - dining table, sofa, kitchen, washing machine. The location is really good too, right in Pera and next to Istiklal street.
I wasn't there on the weekend so can't comment on the noise situation (was fine during my stay) but there are pubs and clubs nearby so if that's not your thing just be aware
The only thing that I would note is that the bathroom doesn't have an extractor fan but it has a window to a vent duct - sometimes the bathroom could get stuffy but it's really not a huge issue. There is also air freshener provided in the bathroom which was a nice touch!
The best thing about the apartment is the host - Derin is super helpful, responsive and kind. He gave me good advice and he is super professional. There is a hotel next to the apartment which Derin manages so it's great that you have a place to turn to for help if you need it. Thank you to Derin (and Engin) for their help and hospitality.
Would definitely recommend booking here and I would love to be back! I would have stayed longer if only it was available!