My intention is to build a modest ESXi 5 server capable of running Lion. What hardware must be compatible? All of it? Just the CPU? Chipset? I've looked through the 10.7.0 HCL, and I don't see any hardware that is 100% compatible without the use of kexts of some sort. For the record, I am aware that ESXi itself has its hardware compatibility limitations of its own.
If anyone else built their own ESXi 5 / Lion box and has gotten it working, would you care to list the hardware you used?
EDIT: In case it's not painfully obvious: Yes, this is my first time with ESXi.
In terms of OS X Lion, need a current or recent Intel C2D or Core i or Xeon 5500 / 5600 processor, ideally a Core i or Xeon 5600 series processor. As the majority of the hardware will be masked by ESXi 5, the only additonal requirement is VT-x enabled in BIOS, as without it you cannot install vanilla Lion under ESXi. Finally a reasonable amount of RAM, depending on what other guestOS's you intend to run on your ESXi box!
In truth any current generation well specified Intel CPU based PC, Workstation or entry level server should be fine, provided it allows for VT-x to be enabled in BIOS, be warned some CPU's that support VT-x may not have the option in BIOS to enable it.
Do not forget you will need another machine to access the Lion guestOS, via VNC or clone or the vSphere Hypervisor Client under Windows, only direct access on the ESXi host is to a text based console for basic configuration and terminal access, obvious but just a reminder if you are new to ESXi.