Hello!
I bought one of the new MacMinis, which were presented yesteraday, plugged two 8GiB DD3-1600 modules in (OsX reported 16GiB of memory, as the models before) and tried to install ESXi 5.1 Build 799733. It started promising:
Initializing chipset...
Initializing timing...
Initializing scheduler...
Initializing processors...
Initializing ACPI...
*BANG*
Pink screen! 
NOT_REACHED bora/vmkernel/hardware/intel/vtd.c:3638
cr0=0x8001003d cr2=0x0 cr3=0x449ad500 cr4=0x12c
*PCPU0:4096/bootstrap
PCPU 0: SISISISISISISIS
Code start: 0x41800c600000 VMK uptime: 0:00:00:04.301
and a stackdump.
I tried instalkling 5.0 and 5.0 U1 also, but with the same result.
It is the regular MacMini with an i7 4C 2.3GHz and one 1TB SATA drive (http://store.apple.com/us/configure/MD388LL/A with no extras), not the MacMini Server.
Any suggestions? Thanks!
PS1: I was unable to boot the ESXi setup from USB key! Since other USB keys (OsX setup for example) didn't work either, I suspect that there's some EFI boot problem from the new USB3 ports. Booting from CD worked, however.
PS2: on the earlies models we had the problem, that the Alt key wasn't recognized after powering on, when there is an USB hub between the keyboard and the Mac (a KVM switch for example). That seems to be fixed now: whenever I press the Alt key at the powerup chime, I get the Apple "boot menu", even with our KVM switch in between.