I am seeing from NewEgg reports that Intel will void your Sandy Bridge warranty if they detect, or you admit to, using anything over 1.55 DRAMv (1.5 +/- 0.05 of ITT). Yes, I find this incredible but I've found 4-5 independent reports that Intel customer service will specifically ask you the dram model and if you report a memory model that is advertised as 1.65v (or if the default JEDEC says so), they will stop the conversation and tell you your processor warranty is voided.
And many of the 1.5v memories exceeds the standard in XMP mode (Corsair Vengeance claims they are the only ones qualified, but I know others have the right specs, at a price). I don't know if they ask what profile you are using.
Yikes! Something to really think about, since many of us are probably running 1.65v dram right now with our Sandy Bridge processors. If you have to call Intel - be prepared.