The Grand Hyatt Seoul is a very very nice hotel. The location is away from everything and has a view of both N Seoul Tower and the Han River. The views are great and the rooms are spacious with very nice amenities (Sofa, comfy bed, renovated bath and robes). The restaurants are really good with nice views, too. In the winter, the front and back are decorated with seasonal lights and the ice skating rink is alive with excitement. I stayed for New Year's Eve and that was an all night event. Pretty awesome because they have their own fireworks display and it is shot into their private space. It is spectacular to see fireworks up close (about 50 meters away). This is one of the few December 31st events in the city and it is worth the won.
The downside are several. One is that the front is not easily accessible if you are wanting to walk to it. The walkway to the road is treacherous because it is on a steep slope and they do not maintain it since it is city property. Another is that you are not greeted when you walk into the lobby. The layout is somewhat awkward because you are not greeted until you walk towards the front desk, located about 25 meters away from the main entryway. A staircase is the first thing you see and there are no signs or personnel to direct you to the front desk. Maybe that is the way it is done in Korea, but I was greeted well when I walked into the JW Marriott in Gangnam. The general manager should be aware of these things, but I don't run the show. Just be aware that you need to seek out the front desk. There is a desk situated between the main entryway and the front desk, but the staff do not acknowledge your presence - not even a simple glance or smile to notice you. I stood in front of 3 men and they ignored me. There is no sign to say who they are or what the desk is for, but I am pretty certain they work there since they had nametags on. After being ignored for 1 full minute (seems forever), I walked past them and then someone approached me to ask if I wanted to check-in. The conceirge is also situated away from the crowd, next to the front desk. A bit out of the way so you need to ask the front desk for the conciege.
Service is what makes a hotel grand, and unfortunately, the Grand Hyatt lacks that, so I give this place a 4 out of 5.

Awesome location in namsan away from the craziness of Itaewon but close enough if you want to venture out there. Brings back some great memories of my "younger" single days living in Seoul. JJ's bar is a classic Seoul night spot for expats and locals alike, crowd is usually pretty decent providing you go on the weekend nights, just be prepared to pay 20 bucks a beer. They also serve a really decent brunch on the weekends. Rooms are comparable to what you'd find at most grand hyatts. If you're there to party at JJ's, I'd recommend going only on the weekends and probably after 10pm in order to avoid the "working" girls there who cater to the older ajashi business men.

The hotel is very nice but is on the side of a relatively small mountain and pretty much isolated from Seoul. One, however, can find plenty of restaurants by either walking down the mountain or taking the hotel shuttle (a walk back may be more exercise than you want, however).

I was in room 1457 which was billed as a king, mountain view (as opposed to a city view costing a little more). In fact, I could see some of the city and the city is plainly visible from the lobby which is all glass on that side of the building. The bed was actually queen size, not king, and it was extremely hard. It had four feather pillows which got pretty flat as the night wore on. The room was clean and very well appointed but very small. My major complaint with the room proper was the total lack of drawer space for clothes. The room had drawers and cabinets but they were used for hotel property, such as the electric kettle, laundry bags, bar glasses, coffee/tea service, safe, shoe care items, etc. I ended up putting my folded clothes on the bottom of the nightstand. The room has good lighting that can be controlled from the bed. There is a desk chair, padded stool and a love seat that faces the head of the bed, so it’s worthless for watching TV. The closet is large with a good number of heavy wooden hangers, ironing board and iron. There is an extra charge for wired and wireless internet. One old school feature of the room that I really liked was a small bedside analog alarm clock with a push button that would cause the face to be illuminated. The desk is a long glass shelf that ran along the window side of the room.

The bathroom didn’t feel cramped and had a long vanity with shelves above so that toiletry storage was not an issue. The towels and wash cloth were thick and more than ample in terms of size. There was no tub, only a shower stall. Curiously, I had little gnat-like bugs in my shower. I’d kill all I could see every time I showered but more appeared the following day. I didn’t report it because they weren’t bothering me and I didn’t want insecticide sprayed in the room while I was there. The floor to the bathroom was elevated about 3” from the room and had a metal lip along the length of the threshold to keep errant water from leaving the bath. I stubbed my toes on the metal lip for a day until I got used to it being there.

I’ve uploaded photos of my room and the view.

I believe there are four restaurants in the hotel. Breakfast was a buffet that was excellent in terms of variety and quality. The only problem was the cost – about US$36. Local beers in the lobby were about US$11 and pints in one of the lower level bars started at $14. We ate at one of the lower level restaurants one evening and the food was fine. It wasn’t cheap but was a bargain in comparison to breakfast.

In summary, if you don’t want to be in a completely urban setting, don’t have a lot of clothes to store and you get reimbursed for meals, you should find this hotel a pleasant retreat.

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The Grand Hyatt Seoul is an excellent hotel with an excellent location if you have business or things to do on the norther shores of the Han river. Otherwise you're better off staying on the other side, in the Gangnam area.
The room is big, bright with a superb view on the Han river. It's on the back side of the hotel so I also had a view on the small ice rink. The spa is very big and luxurious. It's very popular for locals (members) as well as guests. Service is top notch with smiling staff. Breakfast offer a large choice of dishes, both Asian and western choices.
The hotel is situated on top of a hill, not far from the Seoul Tower. I would not recommend walking up if you're not familiar with the area, you could get lost... either use their shuttle (but once of twice per hour is not that convenient) or simply take a cab. It's not that expensive and far more convenient. I'd definitely come back!