Mitsi's place was great! It's very central and very quiet at the same time.
It's also walking distance from the new seafront of Thessaloniki, which for me was the highlight of the city.
The area has many shops and supermarkets nearby for things of everyday use. We didn't use any public transport during our stay, but we saw many bus lines (and I have heard that there is a subway construction nearby.
Overall amazing stay. I would recommend this apt to anyone!