Referencing back to Dan's 4/19 DDMS post with predictions (gotta be one of the Top 10 posts of all times, IMHO), some of the predictions have unfortunately not come true.
For example:
Dan said:
"•Category 4 SPG hotels include the Sheraton Kona Resort & Spa At Keauhou Bay, HI, the Four Points Miami Beach, the Sheraton Brooklyn, the Westin Fort Lauderdale Beach Resort, and the W Beijing...." should be bookable with an "old" Cat1-5 cert. However, all of the above, save for Beijing, have jumped to unified Cat5. With the old Cat1-5 certs becoming usable only for unified Cat1-4, these hotels will be unavailable.
I haven't done the other comparisons yet....