the hotel staff there are very friendly and location is quite convenient (once you know where it is), only a short walk to COEX.
The location is bit hard to find, as it is in a small alley and would be best for the taxi to call the hotel up for directions. No window and the room is quite dim.
With a stay at The Ace Hotel in Seoul (Gangnam), you'll be within a 5-minute drive of COEX Convention and Exhibition Center and Seoul Olympic Stadium. Featured amenities include a 24-hour front desk, an elevator, and coffee/tea in a common area. Self parking (subject to charges) is available onsite.