Just completed a two night stay at the HR Hua Hin.
I took the shuttle bus from GH Erawan both ways; THB600 each way. It was an "interesting" trip! Certainly, the drivers like speed, and weaving in and out of traffic lanes. Felt as though we were on the Brands Hatch circuit! Bit of a bouncy ride, but very convenient and easy. Leaves GH Erawan at 2pm (or thereabouts; I think we actually left around 2:25), and leaves HR Hua Hin to return at 10:00 am (on time). The shuttle makes a "convenience" stop half way (which is good for people like me who have bladders the size of a thimble -

)
I had read this thread from beginning to end prior to booking the hotel. It seems like many of the initial benefits have been eroded over time. I am a Diamond and used a DSU certificate to upgrade. I had a revenue night booked, and then a points night. Had no trouble getting the DSU, and received, what I think is the Regency suite. It was at the far end of the property. The staff very kindly allowed me to keep the suite on the second night (which was an award night).
The suite itself was at the far end of the property, away from the RC, and very close to the tennis court and kids playground. It felt a wee bit claustrophobic in the sense that the patio was hemmed in by bushes and thus had no real view. It was not a large area, and this added to feeling of being penned in. If I stepped off the patio into the "greenery" I could catch a glimpse of the pool. (One disconcerting event - I was taking a "siesta" or rather trying to, when I noticed movement out of the corner of my eye. Reflected in the mirror on the wall near the patio doors was a groundskeeper who was in the greenery. He was watering the plants in my little pen. ) It made me feel very uncomfortable knowing that there was someone right outside the patio. Thankfully the door was locked. Once I saw him, I closed the blinds, but still felt a little vulnerable being alone in the room.
The suite itself was rather minimalist in decor - quite zen like. I liked it, but I can see how some people would feel it to be somewhat sterile (I do agree with that sentiment). I can't give a guess as to the "size" in sq.m, but the living room side was plenty big enough for me! It had a nice sofa and table, and a wet bar area to make tea/coffee or avail oneself of the liquor provided (for a price!).
I received a large plate of tropical fruits, and a bag of pineapple crackers, plus a bag of dried fruit as a welcome gift even though I had elected to take the points rather than amenity. It was a nice gesture and the pineapple crackers came in very handy at 2am when I was wide awake and quite hungry!
The bedroom was as described upthread. Certainly big enough, and quite comfortable. For one or two people, I think it is fine. If you are travelling with more than 1 child it may get a wee bit cramped, especially if you have lots of "stuff" (which is often the case with children - I know it is for me!)
All in all, I liked the suite, it was fine for me. The only thing I didn't like was that it was as far away from the RC club as it could be, and there was no real view of anything. If I were to return to this hotel I wouldn't bother with a suite upgrade; rather, I'd ask for a club deluxe room closer to the RC club and the pools.
The RC club was very pleasant. Open air, cool and a nice place to relax in. When I checked in (and btw I wasn't welcomed with a cool drink and cold towel!), I was given the option of eating breakfast in the Figs restaurant or the RC. I was quite happy with the club offerings. Eggs to order, with bacon, beans, hash browns available. Also pancakes. Fried rice one morning, fried noodles the next. Along with the usual cold cuts,cheeses, fruits, pastries, etc. Completely sufficient, and the service was excellent. The waitstaff were very friendly and helpful. In the evenings, a nice selection of canapes, and wine and beer. The only downside to the RC club is the darned mosquitos. I was eaten alive on both nights, even after spraying myself liberally with the OFF provided in the rooms.
I really enjoyed my brief stay at this property, but think I agree with some posters that it probably needs to be a category lower than it is. I think there is a little bit of hyperbole found in some of the more enthusiastic posts

I used my corporate rate and paid THB 7,565+tax/servicefor the revenue night. Not exactly cheap (but cheaper than the other rates!) and in reality a good deal for what I got- two nights in a suite and the use of the RC club.
GH Erawan is a much better deal for me at THB3,400

but of course, no beach or ocean
I'm a big Hyatt fan, and have yet to find a Hyatt anywhere in the world that, in reality, isn't good. Even the Hyatt Places that I stay at in the US are great value, and always consistent. For the level of property, I'd rather stay in a HP than a CY or HGI.
I think, sometimes, as Diamonds we tend to get a bit picky if things aren't exactly as we want them to be. I know I am truly grateful to be a Diamond and am happy to be able to avail myself of the benefits. Thus, when things are not "perfect" I'm happy to just let it go! (Unless, of course, it is something completely egregious and I've yet to have that happen.)
I plan to be back to Hua Hin at some point in the future, but this time with the Mr.and the Little Miss.
ETA: btw, I would say the property was about 50% capacity. There were a lot of older Brits and Germans vacationing, and a few families with young children. For the most part the kids were pretty good in the club. There was one family who had young boys that were a little rambunctious and I would have liked to have seen the parents control them a little better. Another family who I had traveled down in the minibus with had 3 delightful little girls aged 2,4 and 6 who were impeccably behaved and very sweet to everyone.