I was in SoKo for an event and after staying at the Novatel for a few days, I moved to the JW to get closer to upcoming meetings.

I don't know where to begin - this hotel is incredible.

I was upgraded to an Executive room facing the river on the 30th floor and it was spectacular. Super posh and expansive.
Great restaurants in the hotel - Italian, Japanese, Chinese, American and a Deli. The buffet at "The Cafe" was incredible as were the restaurants that we ate at.
It has the best fitness center and spa I've ever experienced in a hotel.
It located adjacent to Central City, a shopping center. If you go up into the Shinsegae Department Store you'll find high end shopping and more restaurants. If you go down, you'll find continental and local food, coffee, more shops and a bus terminal.

My room was clean, quite and comfortable. Had a hot bath with the bath salts provided and slept like a baby, which was the first good sleep I had on a seven day trip.

The room rate I paid was less expensive than a comparable hotel in the states.

The staff all spoke understandable English and they were all friendly and attentive.

I didn't have time to check out the surrounding area so I'm not sure if there's things to do around the hotel. I did take advantage of the subway station, which is adjacent to the hotel.

I stretched out every minute by asking for a late checkout on my last day. Unfortunately, family back in the states meant I had to head home :) Hopefully we can all go back there as a family someday!

Impressive lobby and larger than normal guest rooms. Excellent mattresses and the sleep quality is wonderful. Staff are very polite.  However, there is a soothness missing from hotel services.  i stayed for 3 days and there were a number of glitches during my visit.  While each one was not terrible and was quickly corrected - the sum of the mistakes would make me look for a different hotel during my next visit. It's a bit long but the highlights are below:
1. Hotel website lists there is a airport bus to hotel (did not mention this bus stops at 21:00). Ok as there was another bus route that dropped off less that 500m away. If I knew cut-off time I would have arranged hotel pick up ahead of time.
2. Arrived at almost midnight and was told that hotel was full. They had upgraded me to a suite (very nice) but asked me not to unpack too much as they would move me to a regular room the next day. I was a bit suprised and must have looked it - they offered to press my suit for the next day at no charge.
3. Moved to regular room the next day which was very nice. When I arrived in the room there was a fruit plate and welcome card. I thought this was a nice gesture given the slightly bumpy arrival and then read the card- name was not mine! So, I called the desk, they apologised, and came to collect the name card but offered me the fruit plate.
4. Went to use the sauna faciliates and there is a 33 000 won charge - even for guests or Marriott members.
5. Late afternoon one day there was a knock at the door and room service brought champagne and ice. I explained I did not order this and they were a bit confused. I had a work meeting on-line later that day - so I knew I had not ordered it ;)
6. I called to confirm the closing time of the dinner buffet - guest services confirmed 22:30. I arrived at 21:00 and was told buffet closed at 21:30.
7. After I checked out I went to one of the restaurants before catching the airport shuttle and wanted to pay for my meal by credit card. The staffperson took my card away and returned with charge to room form. I explained I checked out and need to pay by credit card. She came back and explained I had to sign for the room. So, I signed. 5 minutes later she came back and explained I was not in the room. Now I am a bit frustrated (but not showing it as causing a scene will not help in Asia - plus a bit anxious as I have to catch the shuttle). So, I asked if I could pay at the front and went to the manager there and paid the bill.

As I mentioned earlier, each one of the incidents were not terrible, and I might have similar experiences at other business hotels.  My personal travel is back- packing style and any one of the above would not be an issue on a leisure trip. 

My final impression of the JW Marriott was that all the elements are there to make this a great hotel but not quite running smoothly yet. I might return to the Marriott (as have stayed at Marriott's frequently for business travel and am a member) but, when next in Seoul,  would look for other options to compare.

Excellent in everything, room, amenities, location, staffs.

The room is spacious, a normal JW Marriott style. Extremely convenient for taking subway. Right next to a shopping mall. Staff are very polite. Good for business travel.