Everything was excellent: Kostas welcomed us with a clean flat and he gave us a detailed explanation about where to go and what to do during the time we had in Thessaloniki. He marked all the sites (food, drink, culture) on a map so it was easy to refer to it later on.
I contacted him a few times during the stay and he responded quickly.
It was not a "here are the keys bye" experience but really an introduction to the city from a person living in it.
So all in all, you can go for it!