My husband and I had a very good time in Thessaloniki staying at Dimitri's place for two nights in July.
The apartment has the perfect location - little side street (I believe second door) from the main promenade with many cafes and restaurants. On the other side you are right on the shopping street. The white tower is 5-10 min by foot.
The entrance to the building was not very inviting but the apartment itself was clean and modern, just like on the pictures. We enjoyed the great bed and the fantastic bathroom. The apartment had two air conditioners which was perfect. Unfortunately, the apartment windows don't have a view so we kept them closed - however, we were only there at night and didn't really need a view :)
Dimitri was a very helpful and friendly host. We never met in person, but he always answered all questions right away and it was very easy and convenient to receive codes for the apartment doors instead of a key.
On our check-out day we were able to store all of our belongings in big safes that Dimitri provides for his guests on the first floor of the building. This was really great, so we could spend the day exploring the city without carrying or worrying about our luggage.
Thank you, Dimitri, for hosting us and we recommend your apartment for a stay in Thessaloniki.