We went in celebration of my wife's birthday which was spolied to a large extent by my poor choice of hotel, how was I to know ? .. now you know :)

Pros:

Staff - friendly, helpful
location - especially if you want to go shopping, thought restuarant choice locally was less than average though.
Common areas - lobby etc. well maintained and serviced.

Cons:
room was very tired e.g. tide marks in the bathroom, water damage on the floor, print on TV remote control worn away.
club / business is not 'so exclusive', IMO this is not a business hotel. We were on a Club Floor and surrounded people with either bad manners / no understanding of social etiquette (so you have to question why does the hotel attract this type)
breakfast - poor selection, over crowded breakfast areas. We had to queue / wait to be seated, then poor selection made poorer as it ran out .. and closed at 10 on a Sunday

The hotel is undergoing renovation so it is possible some of the cons will be corrected in time, however I would suggest that the work has quite some way to go.

I spend a lot of my life in 5 star hotels (work related travel) and so my judgement may be swayed by having stayed in quality hotels. I noted on some travel sites that the Westin Chosun is 4 or 4.5 star, 4 star is about right. I imagine the hotel was built in the 80's / early 90's and frankly is struggling to compete with more modern efficient hotels e.g. elevators are slow and massively under capacity (though I have noticed this problem throughout Korea, not an Otis to be seen).

If I'd paid the rack rate I would be fuming, as it stands I find it a waste of my Starwood points.

Rooms a bit on the small side, feel a little cramped. Well-done interior, good quality food from restaurants, if a little overpriced. Breakfast in the basement was a bit grim with flourescent lighting; although food was extensive and generally good.

I just loved it. I usually avoid big hotels and stay in boutiques and B&Bs for the level of service, but this one was just everything we needed. The room was super comfortable - the bed was just superb, I could stay in it all day. The layout of the room was great - the rooms are not big, but very functional and comfortable. The bathroom was also super clean and modern. And the location of the was convenient - 10 min walk to the Metro. We also used the concierge several times and they were truly helpful. As we were traveling to Seoul in the winter, every evening I was looking forward to coming to this hotel and was sad to leave.

Great for tourists as well as business travelers. Deoksu Palace is across the street. Also very close to many shopping places. Internet is too expensive though but there are many nearby places with free wifi. Cheonggye stream is close by and has nice light shows at night and also is a good place to walk during the day.