As Supermicro promised, to me (and to others, such as roberthenderson), they updated their compatibility table appropriately, just as these servers are becoming widely available (mine arrived last week).
I will attempt to reach out to an Intel networking contact (that I met at VMworld 2012), to see if we can learn more about when we can expect support.
Condensed, edited version of the Supermicro compatibility table at
http://www.supermicro.com/support/resources/OS/Broadwell-DE.cfm
Before (June 29th) at left, and after (June 30th) at right.
