Mr. Barbaros' apartment is a perfect place to discover Istanbul. We lived on a fourth floor, but as I understand, there are identical apartments on other three floors as well.
It is quite easy to reach all touristic places in the heart of Instanbul using apartment as a starting point, the only annoying thing is a pretty long (somewhat like 5-10 min) walk up to the hill before reaching the main transport and walking street which is leading to the Sultanahmed square. It is not very awful, but is definitely giving some sporty mood in mornings. On the other hand, Instanbul is built on the hills, so climbing them up and down will be an everyday task anyway, so one hill more is not a big deal.
Mr. Barbaros has his office at the opposite side of the street, and he is quite fast in reacting to messages, so it is easy to reach him if needed and he is very friendly. He spoke with our taxi driver while we've been in the airport and explained him the road, he also ordered the taxi for us for the given time which brought us back. If this is your first trip to Istanbul, taxi is pretty convinient and cheap way to reach the apartments from the airport - somewhat like 50-60 liras, especially if you are not alone.
Apartments have everything necessary, very nice soft beds with this "memory effect" (posh!), and matching the photos pretty well.
When choosing for the floor - from the top one you will see a bit of a sea, but this will cost you 70 steps without an elevator every time. Think twice, lower floors are the same good.
Ah, one more thing about the temperature - we've been there in the end of december/begin of january, and have no problems with the temperature, it was quite comfort even for our habits of having a lot of heaters in Russia. I see other guests commented on this - I might tell it is not really an issue.