My two cents after two days of struggle...

CPU : Intel 3770s

MB : Intel DQ77MK

RAM : 4x8 Gskill

GPU : ATI Radeon 6450 in 16x PCIe

ESXI 5.1: Fail.

No. Way. To get it working.

Both nodes (GPU and HDMI Audio) show up correctly with full names in ESXI.

Card gets detected by Win7 x64, drivers install correctly but... Display never gets detected.

ESXI 5.0u2: Win !

Both nodes show up with "default" device names in ESXI (will come back with a screenshot later), but passthrough works flawlessly on a Win7 x64 VM, through HDMI on a LCD TV. No CEC from the Radeon to use XBMC directly though, what a shame