Thanks, yes, I can confirm that it does, and that booting an EFI shell is as simple as formatting a FAT32 partition on an internal drive, copying the shell binary from the Tiano EFK to \EFI\BOOT\BOOTX64.EFI and enabling UEFI boot from the BIOS. F10 shows an explicit boot option, if needed.
However! the shell reports only EFI 2.0 compliance, using a build from 2008. How can I update this? I have the latest DH55HC BIOS installed, from December 2009.