The very first thing - and to me very important - that I noticed in the apartment was how clean it was. I never really had not so good experience, but this apartment was spotless which I appreciated a lot - thank you.
Further, the apartment is very well equipped if you are staying a bit longer, that means that you would like to prepare your own food etc. - everything from scissors to cloth-pegs (to keep the good coffee pack well closed). The apartment has very nice details and is nicely decorated (look up ;-), just like the whole house as it seemed to me, e.g. the staircase - once you enter the house from the street you will understand what I mean. The boiler must be very modern I think as I only switched it on one time for washing my hair - for the other times, there was still enough warm water for a normal shower. I appreciated the small desk in the bed room for working on my laptop.
There was building noise, yes, but I did not find it too disturbing. The apartment gets warm with high temperatures and due to being in such a city does not cool down easy when the night temperatures do not drop much but in the mornings one can enjoy the first coffee on the balcony.
The apartment itself is set back from direct traffic roads which is a plus. Of course you will still hear some motorcycles etc. but in general I found it rather quite compared to being near such a vibrant hub like Omonia square. I enjoyed to have small shops close, I got the excellent coffee for the coffee machine at Καφεκοπτεία Λουμίδη (and of course some Freddo, too) or the wonderful bakery product from Beneth (Venite). There is a supermarket and organic supermarket just around the corner etc. I also loved to explore the close by areas Exarchion with all its urban art and great cafes or Akademia with all its book and music stores just the same. You can walk to Psyri or Plakka or take the metro - all very accessible from the apartment. As a female solo traveler I did not feel strange at almost any time. Only the area of Vathi and Politechnico will see some sad situations of drug addicts etc. - but again, I did not feel unsafe, or course minding my belongings like in every other city.