Pekatete,
Thanks for this thread.  It tried it on 2 S1's upgraded to S3 with Bitmain's kits and 1 S3.  They all seem to start mining significantly faster after any clock change with the voltage setting of 0750 than with the original (blank) setting.  It also seems to make them more tolerant to higher clock rates.  My S3 did not 'like' clock rates higher than 225 MHz.  It is now stable at 231.25 MHz.  I did not get a chance to make a comparison of power consumption.
I went back to the Oct 2014 f/w on all of these antminers.

Cheers