Efi' apartment was ideally located and really nicely designed. It's located steps from the Acropolis and museum, and is just south of the Plaka shopping district. It's also right off of a metro stop. We were able to walk everywhere we wanted from the apartment. The apartment itself is clean and has balconies which is nice.
The apartment is located up a few flights of steps. There is an elevator but it's very small (fits one person) and a bit old. It was 100% reliable when we used it but my girlfriend was a little uneasy using it.