I stayed there in September 2011 with my family. The apartment is slightly hidden at the back lane, but it has got a 7-eleven at the lobby. Make sure you ask for the location map in Korea language at the reception to show it to the taxi drivers otherwise they will not know where it is.
The apartment comes with kitchenette and washing machine. However, there is no cooking pots and...etc. Unless you request and pay for it.
The washroom is rather small and maybe a little bit too small, but we can live with it.
September (autumn) is a very nice time to visit Seoul, but make sure you closed the window at night because of mosquitos. We all got bitten by them badly!
Breakfast is very simple and not that bad actually, but dont expect any 4-5 star quality and quantity.