I hesitate a lot between 3 stars and 4 stars but in the end I decided to give this place 3 stars -- mainly because of its price. Make no mistake -- this is a very solid choice, and I actually prefer this one to its bigger (and considerably older) sibling that is a few blocks away: Grand Intercontinental. Here are a few points to note:

1. Its location is ideal for exploring the Kangnam area (South of Han River) of Seoul.

It is adjacent to the large underground mall complex called "COEX." You will find all kinds of restaurants, shops, aquarium and cinemas along the busy underground corridors. You won't get bored even if alone. This part of Seoul is very much young, in terms of both construction and people. Also, right in front of this hotel is a nice temple -- a perfect place to stroll and mediate. If you take a cab, you can reach most everywhere in Kangnam in 20 minutes.

2. Rooms are small but neat.

Do not expect any luxury here and tend to be small as well, but they are clean, modern and nicely appointed.

3. Staffs are average.

The staffs are average by most luxury hotel standards: polite and business-like but not going out of way for your concerns.

4. Foods are average.

The Asian Grill on the second floor was by far my favorite: they have a sampling of Asian dishes including Indian. All very authentic. However, the first-floor main buffet falls short of the standard expected of this level hotel. Also, the prices tend to be steep in light of the foods they offer.

In conclusion, Korea is not the best place for value-oriented hotel tourists. The prices are almost on par with those in San Francisco or New York (beverages are much, much more expensive). But I found this one among the more reasonable, although I would prefer its price to be a bit lower considering its level -- although it is rated as a five-star hotel, I can see that it is more like a four-star one.

Excellent experience with hotel stay and hotel staffs. Room was spacious and clean, with enough size of closet and drawers.
I wasn't sure what to prepare for the voltage difference, but I didn't have to worry about it since the room was equipped with 110 V outlets that's separate from 220 V.
It's just that I preferred using public transportation rather than a cab since I love walking on the streets and sightseeing, but I wasn't able to get enough information at the hotel before I went out - even though it was easy to follow signs to subway station, I was hoping to have details in print at the hotel which was not available and I didn't get to learn how to ride a bus without the transportation card thingy even though I asked how to hotel staffs. Also I couldn't get much information for surrounding area for local restaurants or services outside COEX mall.
So, I had to depend on my own research, which was not a problem to me since I speak Korean, but it could have been difficult for non-Korean speakers.
One thing that I would add is that the cakes at the hotel lobby were not that great, and service at that coffee shop didn't match the service quality in general that I enjoyed at the hotel.
Direct KAL limousine bus at incredible rate from and to Incheon airport was a great plus.

I stayed here on a business trip recently. When I arrived, I was pretty impressed by the outlook of the hotel. It was very classy and well-decorated. However, I was a little disappointed with the rooms. Understood that they were undergoing a renovation, and perhaps that's why we got one of the older rooms. The bathroom was not really a pretty sight, just simple, but not one of those luxury bathrooms leaving you wanting more (if you forget your toothbrush, be prepared to pay ALOT for one..! :P). But the beds were really really comfortable, and you could have a choice of cool pillows.

I guess I was expecting a little more, especially with the location. It was a little off from the main areas, like Myeongdong, or Dongdaemun. But really near the companies I had to visit. Business trip I guess.. Heehee! On the upside, COEX was just below us and so was the subway..!

However, I must admit that the staff and the excellent breakfast buffet really made up for it. I wanted to take a trip out to a place that was a little far off. The language barrier was quite bad, but the conceirge, Peter, went out of his way, to ensure that I could get there, get to somewhere central after that, and come back safely. It was so memorable! The next most memorable thing, omg, you've got to try their smoked salmon at breakfast.

It was a good stay!

Coex Intercontinental seemed a very classy hotel, but probably also quite expensive. I don't exactly know, because i've been there invited on a business travel. A bottle of wine there was close to 50 dollars, and for an average breakfast i paid more than 30 dollars. So, the prices are quite high. But i must admit that the conditions there were great and the staff very kind. Also, i recommend to ask at the hotel for taxis as they are careful who they pick. And in town there are few taxis with drivers that speak english. The location didn't seem quite outstanding but you do have there Coex Mall, and all that. Plus, across the street there is a very nice temple that everybody should see.