Even though the SPG50 award is now only 1,000, the description that posts to your account is "50% OFF W/ RES @ 1500 PTS".
I used one at the Westin Sydney a couple of weeks ago and got a reasonably good rate - not that much lower than the lowest rate, but it made a difference over two nights.
As per usual my platinum 500 point amenity didn't post, and neither did the Conde Naste bonus thing.