I think there was quite a bit of discussion about which properties gave you a big "haircut" on exchange rates in the original Costco thread. While it didn't only talk about International properties, they were mentioned regularly.
I also started a thread on MP in February on the subject.
http://milepoint.com/forums/threads/...stco-etc.1551/
Bad Hyatts (10%+)
Park Hyatt when I used them last fall, were by far the worst property. About 15% if I recall right.
Mediocre Hyatts (6-10%)
BKK is pretty bad, usually in the 7-8% range.
GH Seoul 7-8%.
Good Hyatts (1-4%, plus properties that had to be persuaded)
GH Shenzhen is pretty good. I think usually 1.5% or so.
GH Bali, ended up giving normal rate, after offering rate, and then trying to increase it to 8%. Room was booked in USD.
GH Jakarta, ended up giving normal rate, after trying to pull a fast one. Room was booked in USD.
GH SIN was middling, I think it was close to 5%, but will put it in the okay category.
Excellent Hyatts (<1%)
PH Buenos Aires. Gave official rate.
Bali Hyatt. Gave official rate.
Kathmandu Hyatt. Gave official rate.
Most US locations are fine with these certs. Although some now try to disallow their use for corporate rates, AAA rates, etc. The worst that I've run into is the HP North Phoenix.