This Computerworld article has some interesting statistics about Android upgrades. By their research Verizon has the best record for getting Froyo out to their customers, both in the number of different phones upgraded and the time required to get the upgrade out in the wild.
http://www.computerworld.com/s/article/9204798/Android_upgrades_Carrier_comparison?taxonomyId=75&pageNumber=1
The really telling stat is on page 3...only one Samsung phone has the upgrade to Froyo. It seems our long and fruitless wait for Froyo may not be due to Verizon at all but quite likely is due to Samsung being unwilling to bother with support.