The apartment is quite spacious, comfortable and well equipped, with lots of light and air circulation, much appreciated during hot summer days. The beds are comfortable and the shower (bathtub, in fact) has nice water pressure and temperature. Only be aware that -just as most of the old Athenian buildings- there is no wall support for the shower head, which some people might find tricky (in case it does bother you enough, some hardware stores in Athina street sell a removable support with suction pad :-)).
As many other travelers have already mentioned, some corners of the neighbourhood might seem a bit shady for first-time visitors, but as a matter of fact it is quite safe, friendly, lively and practical. There are supermarkets and minimarkets very close; plenty of great restaurants, tavernas and cafes; the Saturday's farmer's market at Kallidromiou; excellent bookstores; the National Archaelogogical Museum and a big nice park, the Pedion Tou Areos, just a few blocks away. Right across the park you can even find a KTEL station with buses to and from Thessaloniki.
Last but not least, communication with Christina was flawless, immediate and receptive. She reacted very quickly to solve a minor inconvenient with the TV and was very flexible to accomodate our check-out time.
Ευχαριστώ πάλι, Χριστίνα!