My guess is that the already Beijing-bound athletes will race for the prize money. I think it will be a race of Olympic-caliber quality for that reason (money). There is enough time between the two races that top athletes can great races at both events. That written, race tactics will be much more of a factor in Des Moines - in my opinion.
Also, it's great for the sport that race directors are stepping up their game to offer big money at these events. Kudos to them.
I can't wait to watch these races on TV. (According to the slowtwitch coverage, the women will be on 5/4, the men on 5/18. Not sure what channel, though probably NBC.)
I think the big factor for Des Moines will be, as you put it Gale, the "big money race." This will mean more pros racing to win. Since these athletes make their living by winning races, will those Americans that are already Beijing-bound be competing? How would that affect race tactics?