Nvidia's cranial-rectal inversion status with partners *OMG!* using something besides Nvidia's standard design hurts them more than they care to know. Nvidia make take the speed crown with Fermi, but they could really deal a hurting if they would loosen up enough to let their partners get creative and release some nice improvements. Of course, when you can barely get the thing to work as-is you wuld be scared to let anyone tinker with it anyway...
Review sites that are generally favorable to Nvidia (read: sold out) get cards before release to put through the paces and have reviews ready at launch. Any other review sites (read: at least partially impartial) have to wait in line and hope for the best.