As previously reported, Intel's first wave of Sandy Bridge-E processors have VT-d (Intel Virtualization Technology for Directed I/O) disabled due to an errata in the C1 stepping. That issue couldn't be resolved in time for the launch but it's getting fixed with the C2 stepping which is set to start rolling out to customers on January 20th, 2012 (samples have already been delivered).
The CPUs moving to the C2 stepping are the hexa-core Core i7-3960X (3.3 GHz) and Core i7-3930K (3.2 GHz). Beside the fixed VT-d, the C2 chips will feature new S-spec and MM numbers so a BIOS update for current motherboards will likely be required.
Is this a big deal? Will I miss out on something if I get a chip that has VT-d disabled?
I don't even know what it is.