Great location since you can head to Taksim from above and the tramway at Fındıklı from below. The location is therefore excellent.
About the flat itself: You need to be ready to walk down a flight of stairs for the washroom and then another flight upstairs for the bedroom. The living room space is small so you would need to take all of your things to the bedroom upstairs. The place is stocked though with necessary and good crockery, glasses, pots and pans. Extra pillows are available. This is fine for two people but you could squeeze in three if you like.