We very much enjoyed our stay in Exarchia, a very lively and interesting neighborhood. Of course, you should know what you expect in an - as to now - not gentrified 'alternative' area, somehow comparable to Kreuzberg, Berlin. Metro (Omonia) or the great Archeological Museum are within walking distance (about 10 min each).
The flat is very clean and quiet (even if there is a street concert around the next corner). Dimitris and Zoi are wonderful hosts. We met Dimitris at arrival and he gave us great tips to restaurants and anything we asked for. Would surely stay again there.