My family has stayed here a number of times. It is not meant to be perfect at the price but it is really good. A little bit hard to find and a little hard to get to, but that can all be managed. The space, the ability to cook meals and the ability to wash clothes in your room make this a great space for a week long stay with two kids. Clean enough and serviced enough. Don't look for room service, but the 7-11 downstairs really does cater for the basic needs.
I would recommend this to any family headed for Seoul!
The park across the street is great for those active kids that we all know and love.

I went with my family of 4 persons in total, staying at a family unit. It is very pleasant! We have kitchen and washing machine for ourselves, spacious beds, fast internet, TV, a window view overlooking the N Seoul Tower. Totally love it! What's more, the buffet breakfast was excellent, too! I especially thought the kimchi served here was very fresh and delicious, and even much better than outside restaurants' kimchi.... There is also a 7-11 store just downstairs at the hotel reception desk; we were surprised to find that the stuff there were not only so conveniently available but actually cheap.

Here is something that I think not many reviews have shared about this hotel. It's a 10-min walk from subway station, but we realized that the best (most efficient and cheapest) way to reach this hotel was to take the airport express train (AREX) (commuter version; 3300KRW/person only; 53minute ride from Incheon airport to Seoul Station) and then a taxi from Seoul station to Hyundai Residence (10-15min ride, ~6000KRW). Before knowing that, we actually took a regular small taxi instead and cost us 65000KRW, which was very expensive, considering that the taxi journey also took 70min, not really faster compared to AREX+short-distance taxi ride (Note: we took the taxi around 9pm, not much traffic jam at that time!). And I suggest that you show the hotel's address in Korean writing to the taxi driver and that will really help him/her inputting the destination address into the car GPS navigation system.

All in all, thumbs up for this hotel!

Stayed there for two nights as family of four. Advanced security and sophisticated electronic locks with video cam seeing who is outside the door. Could rent a full set of cooking utensils for only 1200 wons a night. Very courteous staff and could communicate in English. Only drawback is that it is located in alleys. Seemed dark and would have a little worry when returning late at night.