
Dave from B3D currently has his sample @ 537MHz and rising. This is with just the default cooling (which is a tiny HS/fan). Other sites are reporting 500MHz+ with ease.. 
http://www.beyond3d.com/forum/viewtopic.php?t=5397&postdays=0&postorder=asc&start=0
MuFu.
http://www.beyond3d.com/forum/viewtopic.php?t=5397&postdays=0&postorder=asc&start=0
MuFu.