EDIT: I have an Intel DX79TO board tested working with VT-d passthrough to VMware ESXi5. I've used multiple Core i7 38xx processors, and they have all worked so far.
I know that there were rumors floating around late last year that C1 stepping processors with the X79 chipset had broken support for VT-d. There are a few specifications available that list VT-d as being supported on this hardware, but there are also accounts that it doesn't work, and I don't want to waste a lot of money on bleeding-edge hardware that is supposed to have this feature but doesn't.
Has anyone had/does anyone have a link to someone who has had firsthand experience with VT-d working on X79/Core i7 38xx or 39xx hardware?