Wrapping up six nights here, stayed on a mixture of FNCs and Amex FHR bookings (the latter to burn the $200 Plat credits). Grab bag of thoughts:

• We stayed in both a standard 1 King Bed room on the 11th floor (Han River view) and two different 1 King Bed Club Access rooms on the 18th floor (one Han River view, one Mountain View). The Club Access rooms have more recently remodeled bathrooms, and come with a bidet, at the expense of losing the tub from the standard 1 King Bed. I think this is a worthwhile tradeoff. The bathroom from the standard 1 King Bed was definitely a bit dated but more than functional. The views on both sides are quite nice, and I'm glad we got to see both the Han River and Namsan sides of the hotel.
• No suites available during our stays. It seemed like they were at capacity over the weekend, based on what I saw in the app. The check-in area of the lobby can get pretty bustling around check-in time on Friday/Saturday. I see how it is a popular staycation destination for Koreans.
• Every taxi driver will know to come here if you say "Hyatt." (Might need to add a bit of a Korean accent, though.) Makes me wonder how hard it is to get a taxi to go to the Park Hyatt if you are only an English speaker and not showing them an address on your phone, though... lol
• Impressed with the F&B from the club lounge and the free breakfast at The Terrace via FHR. (Asterisk: Mrs. Wilywombat and I do not have the most refined tastes in the world.) The Terrace has lots of variety and everything we tried was good. A nice perk if going the Prive/FHR route. We also ordered room service since we had the 130,000 KRW F&B credit through FHR, and it was also impressive and prompt. The credit was enough for 2 burgers and 2 desserts.
• All of the staff have been very kind, helpful, and accommodating. English abilities have also been quite good across the board. Mrs. Wilywombat speaks conversational Korean but it was nice to know that I could ask anyone something in English and be fine without her.
• Indoor pool size is quite disappointing. I got some lap swimming in, but I really wish there was more than one lane to work with. The online reservation system for booking a timeslot works fine.
• We poked our heads into the sauna (free for Globs). Very nice facility with lots of nice shower/post-shower products to use. We are not really sauna/jjimjilbang people, but a nice perk regardless.
• I will echo others' sentiments that it is not the most convenient destination for tourism. We relied heavily on the 402/405 buses, which have stops just outside of the hotel's front. I didn't necessarily mind this, as I am generally a big public transportation fan and enjoyed getting to experience the bus system, which is quite good. We never had to wait longer than 5-7 minutes for a bus, even at night, which are very impressive headways for a transit-deprived American like myself. But I can see how someone might prefer a hotel that's right on top of a subway station, or one that is generally more accessible and not on top of the hill. We never attempted the walk downhill to the Itaewon subway stop, but I know it's possible based on others' reviews. (The unfortunate tragedy in Itaewon did happen during our stay -- needless to say, I hope something like this never happens again.)

Our decision to stay at the GH Seoul was primarily motivated for cost reasons, as the FNCs covered 2 nights and the FHR rate meant we ultimately paid very little out of pocket. I think it is a good (not great) use of a Cat 1-4 FNC, and if the FHR cash rate continues to stay in the $200 ballpark and you have Plat credits to burn, it is a fairly optimal place to use them. I was willing to make the compromise in location/convenience, but we are overall quite happy with our stay and would return again in the future.