We figured it out. It turns out it was the Hello Time in RSTP. One of the Force10 white papers describes setting the Hello Time to .5 sec which we did. It turns out that is bad. The PowerConnects were at a Hello Time of 2 (the protocol default) and could not be set as low as 0.5. Once we set the Force10s to a Hello Time of 2, the world was happy. 700ms failovers were had by all.