The sleep thing is anoying, but i think its also the fact that PLL voltage can do the most harm to sandybridges if it gets too high. When compared to vcore etc. And you can run a little cooler with it lower too.
To quote Raja on his Maximus IV GENE-Z guide here -
http://www.asusrog.com/forums/showthread.php?2787-Maximus-IV-GENE-Z-BIOS-Guide-OverclockingHe says this:
CPU PLL Voltage: Sets the voltage for the internal phase locked loop. The role of the PLL is to ensure that the output clock of the internal processor frequency synthesizers maintains phase coherency with the reference clock signal (supplied from a clock generator located within the PCH).
Unlike Nehalem/Gulftown architectures, Sandybridge can benefit from a small increase to PLL voltage when running higher CPU multiplier ratios (hence CPU core frequency). As always, caution is advised with regards to over-voltage on this rail – personally I don’t use any more than 1.85V and that too when processors are sub-zero cooled. Excessive PLL voltage can degrade or kill a processor quicker than overvoltage on any other voltage rail.Id say that's pretty much all there is to know about PLL
🙂*EDIT*
Just forgot to mention, i've run with the PLL OV on and off and it seems to never deviate from 1.8v, id only imagine because I haven't over-clocked high enough yet and 1.8v is the default as far as I know. Some peeps are running with a PLL of 1.55v just fine
🙂Id suggest see if your OK with it off as you said, and then if you are, see how low you can take it and just stay there to get all the benefits.
🙂I think the OV is to help those peeps who want 5GHz and cant quite make it without it.